折半查找法

/**  
     * 折半查找又称二分查找,算法复杂度为O(log(n)),但缺点是要求  
     * 待查表为有序表,此算法充分利用了数组的有序性,采用分治策略  
     * 找出待查元素在数组中的位置,若数组中不存在该元素,则返回-1  
     */    
        
    #include <stdio.h>    
        
    int binary_search(int array[], int n, int data)    
    {    
        int low = 0, high = n - 1, mid;    
        
        while(high >= low)    
        {    
            mid = (low + high) / 2;    
        
            if(array[mid] == data)    
                return mid;    
            else if(array[mid] > data)    
                high = mid - 1;    
            else    
                low = mid + 1;    
        }    
        return -1;    
    }    
        
    main()    
    {    
        int array[] = {1, 5, 30, 41, 100, 101};    
        printf("%d\n", binary_search(array, 6, 101));    
        printf("%d\n", binary_search(array, 6, 2));    
    }    
        
    运行结果:    
    5    
    -1

转载于:https://my.oschina.net/u/1012872/blog/127146