C语言基础练习之数组

1，字符串的循环移动

#include <stdio.h>
#include <string.h>
void func(char buf[], int steps)
{
    int i = 0, j = 0, lenth = 0;
    char temp = 0;
    lenth = strlen(buf);
    for (i=0; i<steps; i++)  // 等同于 while (steps--)
    {
        temp = buf[lenth-1];
        for (j=lenth-1; j>0; j--)
        {
            buf[j] = buf[j-1];
        }
        buf[0] = temp;
    }
}

int main(void)
{
    char buf[] = "123456789";
    int steps = 0;
        printf("输入要移动的位数：");
    scanf("%d", &steps);
    printf("buf = [%s].\n", buf);
    func(buf, steps);
    printf("buf = [%s].\n", buf);
    return 0;
}

2，数组的首位对调排序

#include <stdio.h>
void func(int arr[], int lenth)
{
    int i = 0, temp = 0;
    for (i=0; i<lenth/2; i++)
    {
        temp = arr[lenth-1-i];
        arr[lenth-1-i] = arr[i];
        arr[i] = temp;
    }
}
int main(void)
{
    int i = 0;
    int arr[5] = {1, 2, 3, 4, 5};
    //调用函数，首尾元素对调{5, 4, 3, 2, 1}
    func(arr, 5);
    for (i=0; i<5; i++)
    {
        printf("arr[%d] = %d\n",i,arr[i]); 
    }
    return 0;
}

3，二分法查找有序特定元素列

//正确返回数组下标，没有这个数返回-1.
int search_arr_element(int arr[], int left, int right, int data)
{
    //定义保存中间下标的变量
    int mid = 0;
    while (left <= right)
    {   
        //中间下标赋值
        mid = (left + right) / 2;
        //比较符合条件的下标
        if ( data > arr[mid])
        {
            left = mid + 1;
        }
        else if (data < arr[mid])
        {
            right = mid - 1;
        }
        else
        {   
            printf("找到了%d下标%d.\n", data, mid);
            return mid;
        }

    }
    printf("%d查无此数.\n", data);
    return -1;
}
int main(void)
{
    int arr[5] = {2, 5, 8, 11, 13};
    search_arr_element(arr, 0, 4, 11);
    return 0;
}

递归的方式(二分法)

void search(int arr[], int left, int right, int data)
{
    int mid = (left + right) / 2;
    //回归条件（得到正确结果）
    if (data == arr[mid])
    {
        printf("找到数组下标%d的数据%d.\n", mid, data);

        return mid;
    }
    //回归条件（得到非正确结果）
    if (left > right)
    {
        printf("找不到数据%d.\n", data);
        return;
    }
    if (data > arr[mid])
    {
        search(arr, mid+1, right, data);
    }

    if (data < arr[mid])
    {
        search(arr, left, mid-1, data);
    }
}