C语言经典例题

一、古典问题：有一对兔子，从出生后第3个月起每个月都生一对兔子，小兔子长到第三个月后每个月又生一对兔子，假如兔子都不死，问每个月的兔子总数为多少？

#include <stdio.h>
int main()
{
    int month[23];
    int i;
    month[0]=month[1]=1;
    for(i=0;i<24;i++)
    {
        if(i==0 || i==1)
            printf("%2d: 2只\n", i+1);
        else
            month[i]=month[i-1]+month[i-2];
            printf("%2d: %d只\n", i+1, 2*month[i]);     
    }
    getch();
}
        

#include <stdio.h>
int Rabbit(int n)
{
    if (n==1 || n==2)
        return 2;
    else if (n==0)
        return 0;
    else 
        return Rabbit(n-1)+Rabbit(n-2);
}
int main(int i)
{
    printf("输入查寻月份: ");
    scanf("%d",&i);
    printf("%d月: %ld", i, Rabbit(i));
    getch();
}

 二、打印九九乘法表

#include <stdio.h>
int main()
{
    int i,j,temp;
    for (i=1;i<10;i++)
    {
        for(j=1;j<=i;j++)
        {
            temp=i*j;
            printf("%d*%d=%d\t", j, i, temp);
        }
        printf("\n");
    }
    getch();
}

 三、判断是某天是该年第几天

int main()
{
    int n, year, month, day, days, sum;
    int month_day[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
    printf ("请输入\"year month day\": ");
    scanf ("%d %d %d", &year, &month, &day);
    if ((year%400==0) || (year%4==0&&year%100!=0))
        month_day[2]=29;
    for (n=0;n<month;n++)
    {
        days+=month_day[n];
        sum=days+day;
    }
    printf ("该天是：%d", sum);
    getch();
}

 四、求最大公倍数

#include <stdio.h>

int gcd(int, int);
int main()
{
    int a,b,temp;
    
    scanf("%d %d", &a, &b);
    if (a<b)
    {
        temp=a;
        a=b;
        b=a;
    }

    printf("GAD is : %d", gcd(a, b));
    getch();
}

int gcd(int a, int b)
{
    if(!b)
        return a;
    else 
        return gcd(b, a%b);
}

 五、判断回文

#include <stdio.h>  
#include <stdlib.h>  
#include <string.h>  
  
int main()  
{  
    char str[1001];  
    int len, flag, i;  
  
    while(scanf("%s",str) != EOF)  
    {  
        flag = 1;  
        len = strlen(str);  
  
        for(i = 0; i < len/2; i ++)  
        {  
            if(str[i] != str[len - 1 -i])  
            {  
                flag = 0;  
                break;  
            }  
        }  
        if(flag)  
            printf("Yes!\n");  
        else  
            printf("No!\n");  
    }  
  
    return 0;  
}  

六、求s=a+aa+aaa+aaaa+aa...a的值（长整型数据表示范围为4294967296,因此当次数输入超过10次或者：次数为10次且a>3时会发生溢出。）

#include<stdio.h>

int main()
{
    int a,n,i,M;
    long sum;
    printf("请输入一个个位数和运算的次数：\n");
    scanf("%d%d",&a,&n);
    if((n>10)||((n==10)&&(a>3)))
    {    
        printf("error!\n");
        getch();
        return 0;
    }
    if(n==1)
        sum=a;
    else
    {
        M=a*10+a;
        sum=a+M;
        for(i=1;i<(n-1);i++)
        {
            M=M*10+a;
            sum=sum+M;
        }
    }
    printf("结果为：%ld\n",sum);

    getch();
    return 0;

}

 七、利用递归函数调用方式，将所输入的5个字符，以相反顺序打印出来。

#include<stdio.h>
#include<string.h>

void printchar(char *pc,int n)
{
    char *px;
    px=pc-1;
    printf("%c",*pc);
    if(n!=0)
        printchar(px,n-1);

}

int main()
{
    char c[1000];
    int length;
    printf("输入一串字符:\n");
    scanf("%s",c);
    length=strlen(c);
    printchar(&c[length-1],length);
    getch();
    return 0;
}

 八、求字符串的长度

#include<stdio.h>

int str_len(char *p)
{
    int i=0;
    while(*(p+i)!='\0')
        i++;
    return i;
}

int main()
{
    char ps[1000];   //分配一段安全的内存空间
     printf("input a string:\n");
    gets(ps);
    printf("your string:%s, length is %d",ps,str_len(ps));
    getch();
    return 0;
}

 

#include <stdio.h>
#define IN 1 /* inside a word */
#define OUT 0 /* outside a word */
main()
{
    int nw = 0, c, state;
    state = OUT;
    while ((c = getchar()) != '\n') {
        if (c == ' ' || c == '\t')
        state = OUT;
        else if (state == OUT) {
            state = IN;
            ++nw;
        }
    }
    printf("%d\n", nw);
}

 

九.Write an alernative version of squeeze(s1, s2) that deletes each characher in s1 that matches any character in the string s2.

#include <stdio.h>
squeeze(char s1[], char s2[])
{
    int i, j, k=0;
    int flag = 1;
    for (i=0; s1[i] != '\0'; i++) 
    {
        for (j=0 ; s2[j] != '\0' && flag; j++) 
            if (s1[i] == s2[j])
                flag = 0;
        if (flag)
            s1[k++] = s1[i];
        flag = 1;
    }
    s1[k] = '\0';
}


int main(void)
{
    char a[] = "ab";
    char b[] = "ba";
    squeeze(a, b);
    printf("%s", a);
}