#include <stdio.h>

int binarySearch(int nums[], int numsSize, int target)
{
    int left = 0;
    int right = numsSize -1;
    int middle = 0;
    /*若left小于等于right,说明区间中元素不为0*/
    while(left<=right)
    {
        /*更新查找下标middle的值*/
        middle = (left + right) / 2;
        /*此时target可能会在[left,middle-1]区间中*/
        if(nums[middle] > target)
        {
            right = middle- 1;
        }
        /*此时target可能会在[middle + 1, right]区间中*/
        else if(nums[middle] < target)
        {
            left = middle + 1;
        }
        /*当前下标元素等于target值时，返回middle*/
        else if(nums[middle] == target)
        {
            return middle;
        }
    }
    /*若未找到target元素，返回-1*/
    return -1;
}

int main()
{
    int nums[] = {1, 3, 5, 7, 9};
    int numsSize = sizeof(nums) / sizeof(nums[0]); //计算数组中元素的个数
    int target = 7;

    int result = binarySearch(nums, numsSize, target);

    if(result != -1)
    {
        printf("目标元素 %d 的索引位置为 %d\n", target, result);
    }
    else
    {
        printf("未找到目标元素 %d\n", target);
    }

    return 0;
}