## page was renamed from C语言练习
<<TableOfContents>>

= 找出以下程序中的错误并作出解释 =
 1. 输出hello, world并换行
 {{{
#!cplusplus
include <stdio>
main {
    printf(hello, world/n)
}
}}}
 1. 打印华氏温度与摄氏温度的对照表，输出摄氏度保留一位小数
 {{{
#!cplusplus
#include "stdio.h"
main()
{
    lower = 0;
    upper = 300;
    fahr = lower;
    while( fahr <= upper ) {
        celsius = 5 * (fahr - 32)/9;
        printf("%3.0f %6.1f\n", fahr, celsius);
        fahr += step;
    }
}
}}}
 1. 单词计数
 {{{
#!cplusplus
#include <stdio.h>
enum STATUS{IN, OUT};
main() {
    int c, state;
    int nl = nw = nc = 0;
    while( c = getchar() != EOF) {
        ++nc;
        if(c == "\n") ;
            ++nl;
        if(c == ' ' && c == '\n' && c == '\t')
            state = OUT;
        else if(state = OUT)
            state = IN;
            ++nw;
    }
    printf("%d %d %d\n", nl, nw, nc);
}
}}}
 1. 单词计数新版{{{#!cplusplus
#include <stdio.h>
/* 所有的输入分两类字符：
              一是分界符字符，用OUT表示；
              二是非分界符字符，用IN表示
   表示当前字符类别的state, 由OUT 变成 IN 时， 就有一个单词读入; */
enum STATUS{IN, OUT};
main() {
    int c, state;
    int nl,nw,nc;
    nl = nw = nc = 0;
    state = OUT;
    while( (c = getchar()) != EOF) {
        ++nc;
        if(c == '\n')
            ++nl;
        if(c == ' ' || c == '\n' || c == '\t')
            state = OUT;
        else if(state == OUT){
            state = IN;
            ++nw;
        }
    }
    printf("%d %d %d\n", nl, nw, nc);
}
}}}
 1. 求指数 {{{#!cplusplus
#include <stdio.h>
main() {
    int i;
    for(i = 0, i < 10, i++)
        printf("%d %f %f\n", i, power(2.0f, i), power(-3.0f, i));
    return 0;
}
float power(base, n)
{
    int i;
    float p;
    for(i = 1; i < n; ++i)
        p *= base;
    return p;
}
}}}
 1. 读取字符串并求字符串长度
 {{{
#!cplusplus
#include <stdio.h>
int strlen(char s)
{
    int i = 0;
    while(s[++i] != '0') ;
    return i;
}
int getline(char s, int lim)
{
    int c, i;
    for (i = 0; i < lim-1; ++i) {
        if( (c = getchar()) != EOF && c!='\n')
            s[i] = c;
        else
            brake;
    if (c == '\n')
        s[++i] = c;
    s[i] = '\0';
    return i;
}
main()
{
    char s[];
    int len;
    getline(s, 1000);
    len = strlen(s);
    printf("%d:%s", len, s);
}
}}}
 1. 栈的数据定义和操作
 {{{
#!cplusplus
#define MAXVAL 100;
extern int sp = 0;
double val[MAXVAL];
void push(double f) {
    if(sp < MAXVAL)
        val[++sp] = f;
    else
        printf("error: stack full");
}
double pop(void) {
    if(sp >= 0)
        return val[--sp];
    else {
        printf("error: stack empty");
        return 0.0;
    }
}

main() {
    int i;
    for(i = 0; i < 5; i++)
        push(i);
    for(i = 0; i < 5; i++)
        printf("%f", pop(i));
}
}}}
 1. 递归函数打印一个整数
 {{{
#!cplusplus
#include <stdio.h>
void printd(int n) {
    printd(n / 10);
    putchar(n % 10 + '0');
}

main()
{
    int i = 1234;
    printd(i);
}
}}}
 1. 读取整数的函数
 {{{
#!cplusplus
#include <ctype.h>
#include <stdio.h>
char buf[BUFSIZE];
int bufp = 0;
int getch(void); /*从输入流读取一个字符*/
{
    return (bufp>0)?buf[--bufp]:getchar();
}
void ungetch(int c); /*将一个字符放回输入流*/
{
    if(bufp >= BUFSIZE)
        printf("ungetch: too many char\n");
    else
        buf[bufp++] = c;
}
int getint(int *pn)
{
    int c, sign;
    while(isspace( getch()));
    if(!isdigit(c) && c != EOF && c!='+' && c!='-') {
         ungetch(c);
         return 0;
    }
    sign = c == '-' ? -1 : 1;
    if( c == '+' || c == '-')
        c = getch();
    for( pn = 0; isdigit(c); c = getch())
        pn = 10 * pn + c – '0';
    pn *= sign;
    if(c != EOF)
        ungetch(c);
    return c;
}
}}}
= 读程序，写出程序运行的结果 =
 1. {{{
#!cplusplus
#include <stdio.h>
int dec(int *a) {
    return (*a)--;
}
int inc(int a) {
    return a++;
}
main() {
    int x = 1, y;
    y = dec( &x );
    y = inc(x);
    printf("%d\n%d\n", x, y);

}
}}}
 1. {{{
#!cplusplus
#include <stdio.h>
#define min(x,y) (((x)<(y))?(x):(y))
#ifdef EOF
#define square(x)  x*x
#else
#define square(x)  ((x)*(x))
#endif
int main() {
    int a = 1, b = 2;
    printf("%d\n", square(a+b));
    min(a++, b++);
    printf("%d\n ", min(a, b));
}
}}}
 1. {{{
#!cplusplus
#include <stdio.h>
void selectsort(int v[], int n) {
    int i, j, min, temp;
    for( i = 0; i < n-1; i++) {
        min = i;
        for( j = i + 1; j < n; j++)
            if(v[j] < v[min])
                min = j;
        temp = v[min];
        v[min] = v[i];
        v[i] = temp;
    }
}
int main() {
    int i;
    int s[] = { 5, 4, 3, 2, 1};
    selectsort(s, 5);
    for(i = 0; i < 5; i++)
        printf("%3d", s[i]);
}
}}}
 1. 假定int, unsigned是32位的。
 {{{
#!cplusplus
#include <stdio.h>
int bitcount(unsigned x) {
    int b;
    x = ~x;
    for(b = 0; x != 0; x >>= 1)
        if(x & 1)
            b++;
    return b;
}
main() {
    printf("%d\n%d\n%d\n", bitcount( ~ 0xA), bitcount(017), bitcount(255) );
}
}}}
 1. {{{
#!cplusplus
#include <stdio.h>
#define MAXVAL 10
int queue[MAXVAL];
int front = 0;
int back = 0;
int empty() {
    return front == back;
}
int full() {
    return (back + 1)%MAXVAL == front;
}
int size() {
    return (back - front + MAXVAL) % MAXVAL;
}
void enqueue(int v) {
    if(full())
        return;
    queue[back++] = v;
    back = back % MAXVAL;
}
int dequeue() {
    int v;
    if( empty() )
        return 0;
    v = queue[front++];
    front = front % MAXVAL;
    return v;
}
main() {
    int i;
    for(i = 1; !full(); i++)
        enqueue(i);
    print("%d\n", size());
    while(!empty())
        printf("%d\n", dequeue());
}
}}}
 1. {{{
#!cplusplus
#include <stdio.h>
#include <ctype.h>
int stricmp(char s[], char t[]) {
    int i;
    for( i = 0; s[i] != '\0' && t[i] != '\0'; i++)
        if(tolower(s[i]) != tolower(t[i]))
            break;
    return tolower(s[i]) - tolower(t[i]);
}
main() {
    char s1[] = { 'a', 'b', 'c', 'd', '\0'};
    char s2[] = "ABCD";
    char s3[] = "abcde";
    int s1s2 = stricmp(s1, s2);
    int s2s3 = stricmp(s2, s3);
    printf("%s is %s %s\n", s1, s1s2==0 ? "equal to" : s1s2 > 0 ? "great than" : "less than" , s2);
    printf("%s is %s %s\n", s2, s2s3==0 ? "equal to" : s2s3 > 0 ? "great than" : "less than" , s3);
}
}}}
 1. {{{
#!cplusplus
#include <stdio.h>
#define INITVAL 5
int count() {
    static int c = INITVAL;
    return c--;
}
main() {
    int i;
    while(i = count() )
        printf("%d\n", i);
}
}}}
 1. {{{
#!cplusplus
#include <stdio.h>
double mod(double x, double y) {
        return  x - (int)( x / y ) * y;
}
main() {
    printf("%6.1f\n%6.1f\n", mod(23, 3), mod(-36.5, 7.5) );
}
}}}
= 编程题，按要求编写程序 =
 1. 分别编写递归方式和非递归方式的reverse(s)函数，用于将字符串s倒过来
 1. 分别编写递归方式和非递归方式的fact(n)函数，用于计算n的阶乘n!
 1. 分别编写递归方式和非递归方式的combination(m, n)，用于计算组合数
 1. 写一个程序统计输入的空格数，tab数，和换行数。
 1. 编写一个程序，把输入拷贝到输出，把其中连续的多个空格替换成一个空格。
 1. 编写一个程序，把输入中长度超过80个字符的行输出。
 1. 编写一个程序，把输入中每一行末尾的空格或者tab删除。
 1. 编写一个程序，将输入中的水平制表符替换成适当数目的空格，使空格充满到下一个制表符终止位。假设制表符终止位的位置是固定的，每隔10列就会出现一个制表符终止位。
 1. 编写一个程序，把超过50个字符的输入行折成短一些的两行或多行，折行的位置在输入行的第50、100、150……列的位置。
 1. 编写一个程序，把输入拷贝到输出，并替换退格符为\b，替换其中的tab为\t，替换反斜杠为\\，使得原来不可见的字符变得可见。
= 读程序，写出程序运行的结果 =
 1. {{{
#!cplusplus
#include <stdio.h>
int min(int a, int b) {
    return a < b ? a : b;
}
main() {
    int x = -1, y = -2;
    printf("%d", min(x, y));
}
}}}
 1. {{{
#!cplusplus
#include <stdio.h>
int inc(int a) {
    return ++a;
}
main() {
    int x = -1, y;
    y = inc(x);
    printf("%d\n%d", x, y);
}
}}}
 1. {{{
#!cplusplus
#include <stdio.h>
#include <math.h>
#define FALSE 0
#define TRUE 1
#define BOOL int

BOOL prime(int a) {
    int i;
    for( i = 2; i <= sqrt((double)a); i++)
        if( a % i == 0)
            return FALSE;
    return TRUE;
}
main() {
    int x = 37, y = 91;
    printf("%d\n%d", prime(x), prime(y));
}
}}}
 1. {{{
#!cplusplus
#include <stdio.h>
int fibonacci(int a) {
    int i, curr = 1, next = 1, temp;
    for( i = 1; i < a; i++) {
        temp = next + curr;
        curr = next;
        next = temp;
    }
    return curr;
}
main() {
    int i;
    for(i = 1; i < 10; i++)
        printf("%d\t", fibonacci(i));
}
}}}
 1. {{{
#!cplusplus
#include <stdio.h>
main() {
    int x = 2, y = 1; /*assume int is 32-bit*/
    printf("%d", (~x | ~y) + (x ^ y) );
}
}}}
 1. {{{
#!cplusplus
#include <stdio.h>

main() {
    int flag = 0;
    int count = 0;
    int c;
    while( (c = getchar()) != EOF ) {
        if(flag == 0) {
            if(c =='c')
                flag ++;
        }
        else if( flag == 1) {
            if( c == 'z')
                flag ++;
            else
                flag = 0;
        }
        else if( flag == 2) {
            if( c == 'k')
                count ++;
            flag = 0;
        }
    }
    printf("%d", count);
}
}}}
 程序运行后输入{{{czk loves c programming language! czk programs every day!}}}
 1. {{{
#!cplusplus
#include <stdio.h>

main() {
    int x, y;
    x = 0!=4<=1+2*3/4<<1;
    y = (1 << 2 | 0xF0 ) ^ 071 & 8;
    printf("%d\n%d", x, y);
}
}}}
 1. {{{
#!cplusplus
#include <stdio.h>
#define PI 3.14
main() {
    double r;
    for( r  = 1.0; r <= 4.5; r += 1.0) {
        printf("%6.0f%6.2f%6.2f\n", r, PI*r*2, PI*r*r);
}
}
}}}
 1. {{{
#!cplusplus
#include <stdio.h>
enum months{JAN, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT, NOV, DEC};
main() {
    int days[12];
    int i;
    days[JAN] = 31;
    days[FEB] = 28;
    days[MAR] = 31;
    days[APR] = 30;
    days[MAY] = 31;
    days[JUN] = 30;
    days[JUL] = 31;
    days[AUG] = 31;
    days[SEP] = 30;
    days[OCT] = 31;
    days[NOV] = 30;
    days[DEC] = 31;
    for( i  = JAN; i <= DEC; ++i) {
        printf("month %6d has %6d days\n", i, days[i]);
    }
}
}}}
 1. {{{
#!cplusplus
#include <stdio.h>
enum BOOL {FALSE, TRUE};
int isdigit(int c) {
    return c >='0' && c<='9';
}
int islower(int c) {
    return c >='a' && c<='z';
}
int isupper(int c) {
    return c >='A' && c<='Z';
}
int isalpha(int c) {
    return isupper(c) || islower(c);
}
int isspace(int c) {
    return c=='\n' || c=='\t' || c==' ' || c=='\r' || c=='\v' || c=='\f';
}
int isxdigit(int c) {
    return isdigit(c) || (c>='a' && c <='f') || (c>='A' && c<='F');
}
int isalnum(int c) {
    return isalpha(c) || isdigit(c);
}
main() {
int c;
    while( (c = getchar())!=EOF) {
        printf("%2d%2d%2d%2d%2d%2d%2d\n", isdigit(c), islower(c), isupper(c),
            isalpha(c), isspace(c), isxdigit(c), isalnum(c));
    }
}
}}}
输入(共计7个字符)：{{{b =0XF;}}}

= 按要求编写程序 =
 1. 写一个函数reverse(s)，将字符串s反转。比如
 {{{
char s[]="hello";
reverse(s);
}}}
 这时s变成"olleh"
 1. 写一个函数invert(x,p,n)，这个函数将整数x从右数第p位开始的n位反转（0变1，1变0），并将这个值返回。比如：invert(0x72, 4, 3)将返回0x6E.
 1. 请写一个程序分别统计输入当中空格、水平制表符(tab)和换行符(newline)的个数，即程序运行后输入任意一些字符，以Ctrl+Z结束输入，程序输出这些字符中空格的个数、水平制表符的个数以及换行符的个数。
= 找出以下程序中的错误，并作出解释 =
 1. 输出hello, world并换行
{{{
#!cplusplus
include <stdio.h>

main() {

    printf("hello, world/n")

}
}}}
第一行漏了#，应该是#include <stdio.h>

/n应该改成\n

printf语句后面漏了;

 1. 打印华氏温度与摄氏温度的对照表，输出摄氏度保留一位小数
{{{
#!cplusplus
#include <stdio.h>

main()

{

    int fahr;

    int lower, upper, step;

    lower = 0;

    upper = 300;

    fahr = lower;

    while( fahr <= upper ) {

        double celsius = 5 * (fahr – 32)/9;

        printf("%3.0f %6.1f\n", fahr, celsius);

        fahr += step;

    }

}
}}}
step没有赋初值

fahr是整数，格式化串应该对应的%3d而不是%3.0f

5*(fahr - 32)/9为整数，没有保留小数部分，应改为5.0*(fahr - 32.0) / 9.0

 1. 打印华氏温度与摄氏温度的对照表，输出摄氏度保留一位小数
{{{
#!cplusplus
#include <stdio.h>

#define LOWER 0;

#define UPPER 300;

#define STEP 20;

main () {

    int fahr;

    for(fahr = LOWER, fahr <= UPPER, fahr += STEP)

        printf("%3d %6.1f\n", fahr, (5.0/9.0)(fahr-32));

}

}}}
#define宏后面不要有分号

for的三个字句应该用;分开，而不能用,隔开

(5.0/9.0)和(fahr-32)之间应该有*

 1. 把输入字符复制到输出
{{{
#!cplusplus
#include <stdio.h>

main {

    while(c = getchar() != EOF)

        putchar(c);

}
}}}
main函数后面应该有()

while条件应该为(c=getchar())!=EOF

变量c没有定义，应该定义为int c;

 1. 单词计数
{{{
#!cplusplus
#include <stdio.h>

#define OUT 1

#define IN 0

main() {

    int c, state = OUT;

    int nl = nw = nc = 0;

    while((c=getchar()) != EOF) {

        ++nc;

        if(c == '\n')

            ++nl;

        if(c == ' ' && c == '\n' && c == '\t')

            state = OUT;

        else if(state = OUT) {

            state = IN;

            ++nw;

        }

    }

    printf("%d %d %d\n", nl, nw, nc);

}
}}}
int nl = nw = nc = 0;是错误的，应该写为int nl = 0, nw = 0, nc = 0;

c == ' ' && c == '\n' && c == '\t'应该改为c == ' ' || c == '\n' || c == '\t'

state = OUT应该改为state == OUT

 1. 求指数
{{{
#!cplusplus
#include <stdio.h>

main() {

    int i;

    for(i = 0; i < 10; i++)

        printf("%d %f %f\n",i, power(float 2.0f, int i), power(float -3.0f,int i));

    return 0;

}

float power(base, n)

{

    int i;

    float p = 1.0f;

    for(i = 1; i <= n; ++i)

        p *= base;

    return p;

}
}}}
函数power缺少声明

power函数调用的时候参数错误

power函数定义base和n缺少参数

 1. 求字符串长度的函数
{{{
#!cplusplus
int strlen(char s[])

{

    int i = 0;

    while(s[i] != '0')

        ++i;

    return i;

}
}}}
'0'应该改为'\0'

 1. 栈的数据定义和操作
{{{
#!cplusplus
#define MAXVAL 100

extern int sp = 0;

double val[MAXVAL];

void push(double f) {

    if(sp < MAXVAL)

        val[++sp] = f;

    else

        printf("error: stack full");

}

double pop(void) {

    if(sp >= 0)

        return val[--sp];

    else {

        printf("error: stack empty");

        return 0.0;

    }

}
}}}
extern声明变量sp的时候不能赋初值

push函数当中val[sp++] = f;

 1. 递归函数打印一个整数
{{{
#!cplusplus
#include <stdio.h>

void printd(int n) {

    if(n < 0) {

        putchar('-')

        n = -n;

    }

    printd(n / 10);

    putchar(n % 10 + '0');

}
}}}
printd(n/10);语句前应该加上if(n/10)

 1. 读取整数的函数（getch函数和ungetch函数的定义省略）
{{{
#!cplusplus
#include <ctype.h>

int getch(void); /*从输入流读取一个字符*/

void ungetch(int); /*将一个字符放回输入流*/

int getint(int *pn)

{

    int c, sign;

    while(isspace(c = getch()));

    if(!isdigit(c) && c != EOF && c!='+' && c!='-') {

         ungetch(c);

         return 0;

    }

    sign = c == '-' ? -1 : 1;

    if( c == '+' || c == '-')

        c = getch();

    for( *pn = 0; isdigit(c); c = getch())

        pn = 10 * pn + c – '0';

    *pn *= sign;

    if(c != EOF)

        ungetch(c);

    return c;

}
}}}
pn = 10 * pn + c – '0';应该改为*pn = 10 * *pn + c - '0';

= 读程序，写出程序运行的结果 =
 1. 程序
{{{
#!cplusplus
#include <stdio.h>
int inc(int *a) {
    return (*a)++;
}

main() {
    int x = 1, y;
    y = inc( &x );
    printf("%d\n%d\n", x, y);
}
}}}
结果：

{{{
2
1
}}}
 1. 程序
{{{
#!cplusplus
#include <stdio.h>
double fmod(double x, double y) {
        return  x - (int)( x / y ) * y;
}

main() {
    printf("%6.1f\n%6.1f\n", fmod(5.0, 3.0), fmod(-21.0, 5.0) );
}
}}}
结果

{{{
   2.0
  -1.0
}}}
 1. 程序
{{{
#!cplusplus
#include <stdio.h>
int leapyear(int y) {
    return y % 400 == 0 || y % 100 != 0 && y % 4 == 0;
}

main() {
    int low = 1995;
    int high = 2000;
    int i;
    for(i = low; i <= high; ++i)
        printf("Year %d is %s year\n", i, leapyear(i)?"leap":"nonleap");
}
}}}
结果：

{{{
Year 1995 is nonleap year
Year 1996 is leap year
Year 1997 is nonleap year
Year 1998 is nonleap year
Year 1999 is nonleap year
Year 2000 is leap year
}}}
 1. 程序
{{{
#!cplusplus
#include <stdio.h>
int count() {
    static int c = 0;
    return ++c;
}

main() {
    int i;
    for(i = 5; i > 0; i--)
        printf("count called for %d times\n", count());
}
}}}
结果：

{{{
count called for 1 times
count called for 2 times
count called for 3 times
count called for 4 times
count called for 5 times
}}}
 1. 程序
{{{
#!cplusplus
#include <stdio.h>
#include <ctype.h>
int stricmp(char s[], char t[]) {
    int i;
    for( i = 0; s[i] != '\0' && t[i] != '\0'; i++)
        if(tolower(s[i]) != tolower(t[i]))
            break;
    return tolower(s[i]) - tolower(t[i]);
}

main() {
    char s1[] = { 'a', 'b', 'c', 'd', '\0'};
    char s2[] = "ABCD";
    char s3[] = "abc";
    printf("%s and %s are %s equal\n", s1, s2, (stricmp(s1, s2)==0) ? "" : "not");
    printf("%s and %s are %s equal\n", s2, s3, (stricmp(s2, s3)==0) ? "" : "not");
}
}}}
结果：

{{{
abcd and ABCD are  equal
ABCD and abc are not equal
}}}
 1. 程序
{{{
#!cplusplus
#include <stdio.h>
#define MAXVAL 10
int queue[MAXVAL];
int front = 0;
int back = 0;

void enqueue(int v) {
    queue[back++] = v;
    back = back % MAXVAL;
}

int dequeue() {
    int v = queue[front++];
    front = front % MAXVAL;
    return v;
}

main() {
    int i;
    for(i = 1; i <= 3; i++)
        enqueue(i);
    for(i = 0; i < 3; i++)
        printf("%d\n", dequeue());
}
}}}
结果：

{{{
1
2
3
}}}
 1. 程序（此题中假定int和unsigned为32位）
{{{
#!cplusplus
#include <stdio.h>
int bitcount(unsigned x) {
    int b;
    x = ~x;
    for(b = 0; x != 0; x >>= 1)
        if(x & 1)
            b++;
    return b;
}

main() {
    printf("%d\n%d\n%d\n", bitcount( ~ 0xA), bitcount(017), bitcount(255) );
}
}}}
结果

{{{
2
28
24
}}}
 1. 程序
{{{
#!cplusplus
#include <stdio.h>

int weekday(int year, int month, int day) {
        int y, c;
        if(month == 1 || month == 2) {
                month += 12;
                year--;
        }
        y = year % 100;
        c = year / 100;
        return (y + y/4 + c / 4  - 2 * c + 26*(month+1) / 10 + day -1) % 7;
}

int main() {
        int year = 2005;
        int month = 12;
        int day = 25;
        printf("%d\n", weekday(year, month, day));
        switch(weekday(year, month, day)) {
        case 1: case 2: case 3: case 4: case 5:
                printf("this is a work day\n");
                break;
        case 6: case 0:
                printf("this is not a work day\n");
                        break;
        default:
                printf("this day does not exist\n");
        }
}
}}}
结果：

{{{
0
this is not a work day
}}}
 1. 程序
{{{
#!cplusplus
#include <stdio.h>

void bubblesort(int v[], int n) {
    int i, j;
    for( i = n-1; i >= 0; i--)
        for(j = 0; j < i; j++)
            if(v[j] > v[j+1]) {
                int temp = v[j];
                v[j] = v[j+1];
                v[j+1] = temp;
            }
}

int main() {
    int i;
    int s[] = { 5, 4, 3, 2, 1};
    bubblesort(s, 5);
    for(i = 0; i < 5; i++)
        printf("%3d", s[i]);
}
}}}
结果

{{{
  1  2  3  4  5
}}}
 1. 程序
{{{
#!cplusplus
#include <stdio.h>
#define max(x,y) (((x)>(y))?(x):(y))

int main() {
    int a = 5, b = 6;

    printf("%d\n", max(5, 6));
    max(a++, b++);
    printf("%d\n ", max(a, b));
}
}}}
结果

{{{
6
8
}}}
= 程序填空题，按要求填写程序 =
 1. 打印输入的单词长度的直方图
{{{
#!cplusplus
#include <stdio.h>
#define MAXLENGTH 20

main() {
    int c, i, len, max, nlength[MAXLENGTH+1];
    for(i = 0; i <= MAXLENGTH; i++)
        ___________________
    max = 0;
    len = 0;
    while (__(c=getchar()) != EOF__) {
        if( c != ' ' && c!= '\n' && c != '\t') {
            ++len;
        } else if(len != 0) {
            if(len <= MAXLENGTH) {
                __________________
                if(len > max)
                    max = len;
            }
            len = 0;
        }
    }
    for(i = 1; ___________; i++) {
        int j = 0;
        printf("length:%4d count:%4d ", i, nlength[i]);
        for(j = 0; ________________; j++)
            putchar('=');
        putchar('\n');
    }
}
}}}
程序输入：

{{{
Write a program to print a histogram of the lengths of words in its input
}}}
程序输出结果：

{{{
length:   1 count:   2 ==
length:   2 count:   4 ====
length:   3 count:   2 ==
length:   4 count:   0
length:   5 count:   4 ====
length:   6 count:   0
length:   7 count:   2 ==
length:   8 count:   0
length:   9 count:   1 =
}}}
 1. 快速排序
{{{
#!cplusplus
#include <stdio.h>

void swap(int v[], int i, int j);
void qsort(int v[], int left, int right);

int main() {
    int i;
    int v[] = {15, 12, 31, 21 ,45};
    qsort(_____________);
    for(i = 0; i < 5; i++)
         printf("%4d", v[i]);
}

void qsort(int v[], int left, int right) {
    int i, last;
    if(_______________)
        return;
    swap(v, left, (left+right)/2);
    last = left;
    for(i = left + 1; i <= right; i++)
        if(v[i] < v[left])
            swap(v, ++last, i);
    swap(v, left, last);
    qsort(_____________________);
    qsort(_____________________);
}

void swap(int v[], int i, int j) {
    ___________;
    v[i] = v[j];
    v[j] = temp;
}
}}}
程序输出结果

{{{
  12  15  21  31  45
}}}
= 编程题，按要求编写程序 =
 1. 编写一个ackerman函数，这个函数用于计算如下数学公式。编写一个main函数计算并输出A(3, 4)的值
{{{
#!cplusplus
#include <stdio.h.

int ackerman(int m, int n) {
    if(m==0)
        return n+1;
    else if( n == 0)
        return ackerman(m-1, 1);
    else
        return ackerman(m-1, ackerman(m, n-1));
}

int main() {
    printf("%d", ackerman(3,4));
}
}}}
 1. 编写一个程序，将输入中的水平制表符替换成适当数目的空格，使空格充满到下一个制表符终止位。假设制表符终止位的位置是固定的，每隔10列就会出现一个制表符终止位。
{{{
#!cplusplus
#include<stdio.h>
#include<stdlib.h>
#define TABSIZE 10

main()
{
    int c, i;
    int count = 0;
    while((c=getchar())!=EOF) {
        if(c=='\t') {
            int space = TABSIZE - count % TABSIZE;
            for(i = 0; i < space; i++) {
                putchar(' ');
                count ++;
            }
        } else if (c == '\n'){
            putchar(c);
            count = 0;
        } else {
            putchar(c);
            count ++;
        }
    }
}
}}}