找出以下程序中的错误并作出解释
- 输出hello, world并换行
- 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
- 单词计数
1 #include <stdio.h> 2 enum STATUS{IN, OUT}; 3 main() { 4 int c, state; 5 int nl = nw = nc = 0; 6 while( c = getchar() != EOF) { 7 ++nc; 8 if(c == "\n") ; 9 ++nl; 10 if(c == ' ' && c == '\n' && c == '\t') 11 state = OUT; 12 else if(state = OUT) 13 state = IN; 14 ++nw; 15 } 16 printf("%d %d %d\n", nl, nw, nc); 17 }
- 求指数
- 读取字符串并求字符串长度
1 #include <stdio.h> 2 int strlen(char s) 3 { 4 int i = 0; 5 while(s[++i] != '0') ; 6 return i; 7 } 8 int getline(char s, int lim) 9 { 10 int c, i; 11 for (i = 0; i < lim-1; ++i) { 12 if( (c = getchar()) != EOF && c!='\n') 13 s[i] = c; 14 else 15 brake; 16 if (c == '\n') 17 s[++i] = c; 18 s[i] = '\0'; 19 return i; 20 } 21 main() 22 { 23 char s[]; 24 int len; 25 getline(s, 1000); 26 len = strlen(s); 27 printf("%d:%s", len, s); 28 }
- 栈的数据定义和操作
1 #define MAXVAL 100; 2 extern int sp = 0; 3 double val[MAXVAL]; 4 void push(double f) { 5 if(sp < MAXVAL) 6 val[++sp] = f; 7 else 8 printf("error: stack full"); 9 } 10 double pop(void) { 11 if(sp >= 0) 12 return val[--sp]; 13 else { 14 printf("error: stack empty"); 15 return 0.0; 16 } 17 } 18 19 main() { 20 int i; 21 for(i = 0; i < 5; i++) 22 push(i); 23 for(i = 0; i < 5; i++) 24 printf("%f", pop(i)); 25 }
- 递归函数打印一个整数
- 读取整数的函数
1 #include <ctype.h> 2 #include <stdio.h> 3 char buf[BUFSIZE]; 4 int bufp = 0; 5 int getch(void); /*从输入流读取一个字符*/ 6 { 7 return (bufp>0)?buf[--bufp]:getchar(); 8 } 9 void ungetch(int c); /*将一个字符放回输入流*/ 10 { 11 if(bufp >= BUFSIZE) 12 printf("ungetch: too many char\n"); 13 else 14 buf[bufp++] = c; 15 } 16 int getint(int *pn) 17 { 18 int c, sign; 19 while(isspace( getch())); 20 if(!isdigit(c) && c != EOF && c!='+' && c!='-') { 21 ungetch(c); 22 return 0; 23 } 24 sign = c == '-' ? -1 : 1; 25 if( c == '+' || c == '-') 26 c = getch(); 27 for( pn = 0; isdigit(c); c = getch()) 28 pn = 10 * pn + c – '0'; 29 pn *= sign; 30 if(c != EOF) 31 ungetch(c); 32 return c; 33 }
读程序,写出程序运行的结果
1 #include <stdio.h> 2 void selectsort(int v[], int n) { 3 int i, j, min, temp; 4 for( i = 0; i < n-1; i++) { 5 min = i; 6 for( j = i + 1; j < n; j++) 7 if(v[j] < v[min]) 8 min = j; 9 temp = v[min]; 10 v[min] = v[i]; 11 v[i] = temp; 12 } 13 } 14 int main() { 15 int i; 16 int s[] = { 5, 4, 3, 2, 1}; 17 selectsort(s, 5); 18 for(i = 0; i < 5; i++) 19 printf("%3d", s[i]); 20 }
- 假定int, unsigned是32位的。
1 #include <stdio.h> 2 #define MAXVAL 10 3 int queue[MAXVAL]; 4 int front = 0; 5 int back = 0; 6 int empty() { 7 return front == back; 8 } 9 int full() { 10 return (back + 1)%MAXVAL == front; 11 } 12 int size() { 13 return (back - front + MAXVAL) % MAXVAL; 14 } 15 void enqueue(int v) { 16 if(full()) 17 return; 18 queue[back++] = v; 19 back = back % MAXVAL; 20 } 21 int dequeue() { 22 int v; 23 if( empty() ) 24 return 0; 25 v = queue[front++]; 26 front = front % MAXVAL; 27 return v; 28 } 29 main() { 30 int i; 31 for(i = 1; !full(); i++) 32 enqueue(i); 33 print("%d\n", size()); 34 while(!empty()) 35 printf("%d\n", dequeue()); 36 }
1 #include <stdio.h> 2 #include <ctype.h> 3 int stricmp(char s[], char t[]) { 4 int i; 5 for( i = 0; s[i] != '\0' && t[i] != '\0'; i++) 6 if(tolower(s[i]) != tolower(t[i])) 7 break; 8 return tolower(s[i]) - tolower(t[i]); 9 } 10 main() { 11 char s1[] = { 'a', 'b', 'c', 'd', '\0'}; 12 char s2[] = "ABCD"; 13 char s3[] = "abcde"; 14 int s1s2 = stricmp(s1, s2); 15 int s2s3 = stricmp(s2, s3); 16 printf("%s is %s %s\n", s1, s1s2==0 ? "equal to" : s1s2 > 0 ? "great than" : "less than" , s2); 17 printf("%s is %s %s\n", s2, s2s3==0 ? "equal to" : s2s3 > 0 ? "great than" : "less than" , s3); 18 }
编程题,按要求编写程序
- 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
- 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!
- 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
- 写一个程序统计输入的空格数,tab数,和换行数。
- 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。
- 编写一个程序,把输入中长度超过80个字符的行输出。
- 编写一个程序,把输入中每一行末尾的空格或者tab删除。
- 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。
- 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。
- 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 #include <stdio.h> 2 #include <math.h> 3 #define FALSE 0 4 #define TRUE 1 5 #define BOOL int 6 7 BOOL prime(int a) { 8 int i; 9 for( i = 2; i <= sqrt((double)a); i++) 10 if( a % i == 0) 11 return FALSE; 12 return TRUE; 13 } 14 main() { 15 int x = 37, y = 91; 16 printf("%d\n%d", prime(x), prime(y)); 17 }
1 #include <stdio.h> 2 3 main() { 4 int flag = 0; 5 int count = 0; 6 int c; 7 while( (c = getchar()) != EOF ) { 8 if(flag == 0) { 9 if(c =='c') 10 flag ++; 11 } 12 else if( flag == 1) { 13 if( c == 'z') 14 flag ++; 15 else 16 flag = 0; 17 } 18 else if( flag == 2) { 19 if( c == 'k') 20 count ++; 21 flag = 0; 22 } 23 } 24 printf("%d", count); 25 }
程序运行后输入czk loves c programming language! czk programs every day!
1 #include <stdio.h> 2 enum months{JAN, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT, NOV, DEC}; 3 main() { 4 int days[12]; 5 int i; 6 days[JAN] = 31; 7 days[FEB] = 28; 8 days[MAR] = 31; 9 days[APR] = 30; 10 days[MAY] = 31; 11 days[JUN] = 30; 12 days[JUL] = 31; 13 days[AUG] = 31; 14 days[SEP] = 30; 15 days[OCT] = 31; 16 days[NOV] = 30; 17 days[DEC] = 31; 18 for( i = JAN; i <= DEC; ++i) { 19 printf("month %6d has %6d days\n", i, days[i]); 20 } 21 }
1 #include <stdio.h> 2 enum BOOL {FALSE, TRUE}; 3 int isdigit(int c) { 4 return c >='0' && c<='9'; 5 } 6 int islower(int c) { 7 return c >='a' && c<='z'; 8 } 9 int isupper(int c) { 10 return c >='A' && c<='Z'; 11 } 12 int isalpha(int c) { 13 return isupper(c) || islower(c); 14 } 15 int isspace(int c) { 16 return c=='\n' || c=='\t' || c==' ' || c=='\r' || c=='\v' || c=='\f'; 17 } 18 int isxdigit(int c) { 19 return isdigit(c) || (c>='a' && c <='f') || (c>='A' && c<='F'); 20 } 21 int isalnum(int c) { 22 return isalpha(c) || isdigit(c); 23 } 24 main() { 25 int c; 26 while( (c = getchar())!=EOF) { 27 printf("%2d%2d%2d%2d%2d%2d%2d\n", isdigit(c), islower(c), isupper(c), 28 isalpha(c), isspace(c), isxdigit(c), isalnum(c)); 29 } 30 }
输入(共计7个字符):b =0XF;
按要求编写程序
- 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" - 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.
- 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。一个程序可能有多个错误。如果没有错误,请注明程序正确。(每小题3分,共30分)
- 输出hello, world并换行
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;
- 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
#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
- 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
#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*
- 把输入字符复制到输出
#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;
- 单词计数
#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;
- state = IN; ++nw;
- ++nc; if(c == '\n')
}
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
- 求指数
#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));
}
float power(base, n)
{
- int i; float p = 1.0f;
for(i = 1; i <= n; ++i)
- p *= base;
}
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
- 求字符串长度的函数
int strlen(char s[])
{
- int i = 0; while(s[i] != '0')
- ++i;
}
'0'应该改为'\0'
- 栈的数据定义和操作
#define MAXVAL 100
extern int sp = 0;
double val[MAXVAL];
void push(double f) {
if(sp < MAXVAL)
- val[++sp] = f;
- printf("error: stack full");
}
double pop(void) {
if(sp >= 0)
- return val[--sp];
- 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;
- 递归函数打印一个整数
#include <stdio.h>
void printd(int n) {
if(n < 0) {
- putchar('-') n = -n;
}
printd(n/10);语句前应该加上if(n/10)
- 读取整数的函数(getch函数和ungetch函数的定义省略)
#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;
if( c == '+' || c == '-')
- c = getch();
- pn = 10 * pn + c – '0';
- pn *= sign; if(c != EOF)
- ungetch(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(每小题3分,共30分)
- 程序
#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
- 程序
#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
- 程序
#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
- 程序
#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
- 程序
#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;
- if(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
- 程序
#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
- 程序(此题中假定int和unsigned为32位)
#include <stdio.h>
int bitcount(unsigned x) {
- int b; x = ~x;
for(b = 0; x != 0; x >>= 1)
if(x & 1)
- b++;
}
main() {
- printf("%d\n%d\n%d\n", bitcount( ~ 0xA), bitcount(017), bitcount(255) );
}
结果
2
28
24
- 程序
#include <stdio.h>
int weekday(int year, int month, int day) {
- int y, c;
if(month == 1 || month == 2) {
- month += 12; year--;
}
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;
- printf("this is not a work day\n");
- break;
- printf("this day does not exist\n");
}
结果:
0
this is not a work day
- 程序
#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
- 程序
#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(每空2分,共20分)
- 打印输入的单词长度的直方图
#include <stdio.h>
#define MAXLENGTH 20
main() {
- int c, i, len, max, nlength[MAXLENGTH+1];
for(i = 0; i <= MAXLENGTH; i++)
nlength[i] = 0;
while ((c=getchar()) != EOF) {
if( c != ' ' && c!= '\n' && c != '\t') {
- ++len;
if(len <= MAXLENGTH) {
nlength[len]++;
if(len > max)
- max = len;
for(i = 1; i <= max; i++) {
- int j = 0; printf("length:%4d count:%4d ", i, nlength[i]);
for(j = 0; j < nlength[i]; j++)
- putchar('=');
}
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 =
- 快速排序
#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(v, 0, 4);
for(i = 0; i < 5; i++)
- printf("%4d", v[i]);
}
void qsort(int v[], int left, int right) {
- int i, last;
if(left >= right)
- return;
for(i = left + 1; i <= right; i++)
if(v[i] < v[left])
- swap(v, ++last, i);
qsort(v, left, last - 1);
qsort(v, last + 1, right);
}
void swap(int v[], int i, int j) {
int temp = v[i]; 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(每小题10分,共20分)
- 编写ackerman函数
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
#include <stdio.h.
int ackerman(int m, int n) {
- if(m==0)
- return n+1;
- return ackerman(m-1, 1);
- return ackerman(m-1, ackerman(m, n-1));
}
int main() {
- printf("%d", ackerman(3,4));
}
- 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。
#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 ++;
- putchar(c); count = 0;
- putchar(c); count ++;
- int space = TABSIZE - count % TABSIZE;
- if(c=='\t') {
}