折半查找算法

Posted 2021-01-21 tedani

#include <stdio.h>

int halfIntervalSearch(int *p, unsigned int len, int num)
{
    unsigned int highSN = len-1;
    unsigned int lowSN = 0;
    unsigned int midSN = 0;
    int ret = -1;

    //lowSN与highSN折半法无限靠近，直至lowSN==highSN找到。
    //一旦找不到，则当lowSN==highSN后，lowSN继续+1 or highSN继续-1，直到lowSN > highSN退出
    while (lowSN <= highSN)
    {
        midSN = (lowSN + highSN)/2;

        if (num == p[midSN])
        {
            ret = midSN;
            break;
        }
        else if (num > p[midSN])
        {
            lowSN = midSN + 1;
        }
        else if (num < p[midSN])
        {
            highSN = midSN - 1;
        }
    }

    return ret;
}

void main(void)
{
    int numberTable[] = {2,47};
    int sn = -1;
    
    sn = halfIntervalSearch(numberTable, sizeof(numberTable)/sizeof(int), 47);
    printf("find sn number: %d ", sn);
}