在整形有序陣列中查詢想要的數字，找到了返回下標，找不到返回-1.

#include<stdio.h>
int main(){
	double arr[] = { 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 };
	int to_find = 7;
	int left = 0;
	int right = sizeof(arr) / sizeof(arr[0]) - 1;
	int mid = 0;
	while (left <= right){
		mid = (left + right) / 2;
		if (to_find < arr[mid]){
			right = mid - 1;
		}
		else if (to_find>arr[mid]){
			left = mid + 1;
		}
		else{
			break;
		}
	}if (left<=right){
		printf("%d\n", mid);
	}
	else{
		printf("-1");
	}
	system("pause");
	return(0);
}