C语言 - 折半查找

算法复杂度O(logn)

#include

#define MAX_N 100

//实现单调递增 数组arr中查询数字x是否存在
//数组长度为n，如果找到了，返回x所在数组下标，否则返回1 
int binary_search(int *arr, int x, int n){
	int min = 0;
	int max = n-1;
	int mid;
	while(min <= max){
		//或 mid = (min + max) >> 1;
		mid	= (min + max) / 2;
		if(arr[mid] == x){
			return mid;
		}else if(arr[mid] > x){
			max = mid - 1;
		}else{
			min = mid + 1;
		}
	}
	return -1;
}

int main(){
	int arr[MAX_N + 5] = {0};
	int n;
	scanf("%d", &n);
	for(int i = 0; i < n; i++){
		//arr+i 可以替换为 &arr[i] 
		scanf("%d", arr+i);
	}
	int x;
	while(~scanf("%d", &x)){
		printf("search %d from array:%dn", x, binary_search(arr, x, n));
	}
	return 0;
}