C语言实现二分查找

　　二分查找优势:比顺序查找更有效率
       特点:元素按顺序排列

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
int main()
{
    int a[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
    int left = 0;
    int right = sizeof(a) / sizeof(a[0])-1;
    int target = 0;
    printf("请输入你想查的数字:");
    scanf("%d", &target);
    while (left<=right){
        int mid = (left + right) / 2;
        if (mid > target)
        {
            right = mid - 1;
        }
        else if (mid < target)
        {
            left = mid + 1;
        }
        else if (mid == target)
        {
            printf("目标函数下标是:%d\n",mid);
            break;
        }
    }
    if (right < left)
    {
        printf("你想查的数字没有找到!\n");
    }
    system("pause");
}