二分查找

#include <stdio.h>
//LENGTH 为有序表长度 
#define LENGTH 100 

//
int binarySearch(int a[], int value, int len){
	int low = 0;
	int high = len - 1;
	int mid = 0;
	while(low <= high){		
		mid = low + (high - low) / 2; //注意此处，如果写为mid=(low+high)/2的话，容易导致溢出。 
		if(value == a[mid]){
			return mid;
		}else{
			//printf("low:%d, mid:%d, high:%d \n", low, mid, high);
			if(value < a[mid]){
				high = mid - 1;
			}else{
				low = mid + 1;
			}
		}
	}
	return -1;
}

int main(){
	
	int array[LENGTH] = {0};
	int i = 0;
	int length = 0;
	int value;

	//测试 
	while(scanf("%d %d", &length, &value)!=EOF){
		for(i = 0; i < length; i++){
			array[i] = 10 * i;
		}
		printf("%d	\n", binarySearch(array, value, length));
	}
	return 1;
}