C语言数组练习

位运算符是对字节或字中的实际二进制位操作的，只能操作二进制
两行scanf（）中间有时要用getchar(); //滤掉回车符
strlen ( )函数求字符串长度，如果字符串是用户输入的，则不能提前声明，要放在输入之后求取

1.有n个人围成一圈,顺序排号,从第一个开始报数(从1到3报数),凡报到3的人退出圈子,问最后最后留下的是原来第几号的那位.

#include <stdio.h>

int main()
{
    int n, i, m = 0, k = 0;
    int a[500];

    printf("Please input n:");
    scanf("%d", &n);

    for(i = 0; i < n; i++ )
    {
        a[i] = i + 1;
    }

    while(m < n-1)
    {
        for(i = 0; i < n; i++)
        {
            if(a[i] != 0)
            {
                k++;
                if(k%3 == 0)
                {
                    a[i] = 0;
                    m++;
                }
            }
        }
    }

    for(i = 0; i < n; i++)
    {
        if(a[i] != 0)
            printf("The last one is:%d\n", a[i]);
    }
    return 0;
}

2.字符数组中在指定位置插入字符

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

int main() 
{
    char str[20] = {0};
    char b[20] = {0};
    int m, i, length;
    int j = 0;
    char c;

    printf("请输入字符串：");
    scanf("%s", str);
    getchar();
    printf("请输入插入位置：");
    scanf("%d", &m);
    getchar();   //消除enter影响
    printf("请输入插入元素：");
    scanf("%c",&c);
    length = strlen(str);

    for(i = m-1; i <= length; i++)
    {
        b[j] = str[i];
        j++;
    }

    str[m-1] = c;
    j = 0;

    for(i = m; i <= length; i++)
    {
        str[i] = b[j];
        j++;
    }

    printf("结果：%s\n", str);
    return 0;

}

3.在字符数组中指定开始位置插入字符串

法一：

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

int main() //字符数组中在指定位置插入字符串
{
    char a[20] = {0};
    char b[20] = {0};
    char c[20] = {0};
    int i, j = 0, n, lengtha, lengthb, lengthc;

    printf("请输入字符串：");
    scanf("%s", a);
    getchar();
    printf("请输入插入字符串：");
    scanf("%s", b);
    getchar();
    printf("请输入插入位置：");
    scanf("%d", &n);
    getchar();
    lengtha = strlen(a);
    lengthb = strlen(b);

    for(i = n; i < lengtha; i++)
    {
        c[j] = a[i];
        j++;
    }
    lengthc = j;
    j = n;

    for(i = 0; i < lengthb; i++)
    {
        a[j] = b[i];
        j++;
    }

    for(i = 0; i < lengthc; i++)
    {
       a[j] = c[i];
       j++;
    }

    printf("结果：%s\n",a);

    return 0;
}

法二：

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

int main()
{
    char a[100] = {0}, b[10] = {0};
    int lengtha, lengthb, i;
    int num;

    printf("Please input:");
    scanf("%s %d%s", a, &num, b);
    lengtha = strlen(a);
    lengthb = strlen(b);

    for(i = lengtha; i >= num; i--)
    {
        a[i + lengthb] = a[i];
    }
    strncpy(a+num, b, num);
    printf("%s\n", a);
    return 0;
}

法三：

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

int main()
{
    char a[20] = "helloworld";
    char b[20], str[20], ptr[20];
    int i;

    printf("Please input the address:");
    scanf("%d", &i);
    getchar();
    printf("Please input the char:");
    scanf("%s", ptr);

    strcpy(str, a + i - 1);
    strcat(ptr, str);
    strncpy(b, a, i - 1);
    b[i - 1] = '\0';      //strncpy复制前n个字符，不一定包含\0
    strcat(b, ptr);
    printf("%s", b);
    return 0;
}

C语言 数组练习

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