二分查找

 

/*
 * 二分查找
 * Lzy 2011-5-28
 */

#include <stdio.h>
#define N 8

int BinSearch(int X[],int n, int K)            /*二分查找*/
{                                /*X待查数组，n长度，k要查找的关键值*/
    int low = 0, high = n-1;
    int mid;

    while(low <= high)                /*等于必须要*/
    {
        mid = (low + high) / 2;

        if(X[mid] == K)
            return X[mid];            /*查找成功*/
        if(X[mid] < K)                /* 中间位置的数据元素小于关键字 */
            low = mid + 1;            /*在右边查找*/
        else
            high = mid - 1;            /*在左边查找*/
    }
    return -1;                        /*查找失败*/
}


int main(void)
{
    int i;
    int X[N] = {1,2,3,4,5,6,7,8};
    i = BinSearch(X,8,5);

    printf("%d\n",i);
}