二分

#include <stdio.h>
//A[]为严格递增序列，left为二分下界，right为二分上界，x为欲查询的数
//二分区间为左闭右闭得[left, right],传入的初值为[0,1]
int binarySearch(int A[], int left, int right, int x) {
	int mid;
	while(left <= right){
		mid = (left + right) / 2;
		if(A[mid] == x)
			return mid;
		else if(A[mid] > x)
			right = mid - 1;
		else
			left = mid + 1; 
	}
	return -1;
}
int main() {
	int A[10] = {1, 3, 4, 6, 7, 8, 10, 11, 12, 15};
	printf("%d", binarySearch(A, 0, n - 1, 6));
	return 0;
}