#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <stdlib.h>
int research(int arr[], int goal, int left, int right){
	while (left <= right){
		int mid = left + ((right - left) / 2);//求出中间元素的位置
		if (goal<arr[mid]){
			right = mid - 1;
		}
		if (goal>arr[mid]){
			left = mid + 1;
		}
		if (goal==arr[mid]){
			return mid;
		}
	}
	return -1;
}
int main(){
	int arr[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
	int left = 0;
	int right = (sizeof(arr) / sizeof(arr[0])) - 1;
	int ret=research(arr, 4, left, right);
	if (ret == -1){
		printf("没有这个数\n");
	}
	else
		printf("这个数的下标为：%d\n", ret,);
	system("pause");
	return 0;

}