C语言练习1
找出以下程序中的错误并作出解释
- 输出hello, world并换行
include <stdio>
main {
printf(hello, world/n)
}- 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()
{
lower = 0;
upper = 300;
fahr = lower;
while( fahr <= upper ) {
celsius = 5 * (fahr - 32)/9;
printf("%3.0f %6.1f\n", fahr, celsius);
fahr += step;
}
}- 单词计数
#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);
}- 单词计数新版
#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);
}- 求指数
#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;
}- 读取字符串并求字符串长度
#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);
}- 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;
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));
}- 递归函数打印一个整数
#include <stdio.h>
void printd(int n) {
printd(n / 10);
putchar(n % 10 + '0');
}
main()
{
int i = 1234;
printd(i);
}- 读取整数的函数
#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
#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);
}#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));
}#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]);
}- 假定int, unsigned是32位的。
#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) );
}#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());
}#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);
}#include <stdio.h>
#define INITVAL 5
int count() {
static int c = INITVAL;
return c--;
}
main() {
int i;
while(i = count() )
printf("%d\n", i);
}#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
- 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，并替换退格符为替换其中的tab为替换反斜杠为\，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
#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));
}#include <stdio.h>
int inc(int a) {
return ++a;
}
main() {
int x = -1, y;
y = inc(x);
printf("%d\n%d", x, y);
}#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));
}#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));
}#include <stdio.h>
main() {
int x = 2, y = 1; /*assume int is 32-bit*/
printf("%d", (~x | ~y) + (x ^ y) );
}#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!#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);
}#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);
}
}#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]);
}
}#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
- 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
- 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
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;
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 == ‘’ && c == ‘应该改为c ==’ ’ || c == ‘’ || c == ’
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));
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
- 求字符串长度的函数
int strlen(char s[])
{
int i = 0;
while(s[i] != '0')
++i;
return 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;
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;
- 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);
putchar(n % 10 + '0');
}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;
}
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
- 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;
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- 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++;
return 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--;
}
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- 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
- 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++)
___________________
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 =- 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(_____________);
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
- 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;
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));
}- 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 ++;
}
} else if (c == '\n'){
putchar(c);
count = 0;
} else {
putchar(c);
count ++;
}
}
}