纪念逝去的岁月——C/C++二分查找

代码

#include <stdio.h>



int binarySearch(int iList[], int iNum, int iX, int * pPos)

{

    if(NULL == pPos)

    {

        return -1;

    }

    int i = 0, j = iNum;

    while(i < j)

    {

        printf("from [%d] to [%d]\n", i, j);

        int iPos = (i + j) / 2;

        int iMid = iList[iPos];

        if(iX == iMid)

        {

            *pPos = iPos;

            return 0;

        }

        else if (iX > iMid)

        {

            i = iPos + 1;

        }

        else

        {

            j = iPos - 1;

        }

    }

    if(iList[i] == iX)

    {

        *pPos = i;

        return 0;

    }

    *pPos = -1;

    return -1;

}



int main(int argc ,char * argv[])

{

    int iList[33] = {0, 1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33};

    int iPos = 0;

    int iNum = 33;



    int iX = 5;

    binarySearch(iList, iNum, iX, &iPos);

    printf("[%d] @ position [%d]\n\n", iX, iPos);



    iX = 6;

    binarySearch(iList, iNum, iX, &iPos);

    printf("[%d] @ position [%d]\n\n", iX, iPos);



    iX = 0;

    binarySearch(iList, iNum, iX, &iPos);

    printf("[%d] @ position [%d]\n\n", iX, iPos);



    iX = 33;

    binarySearch(iList, iNum, iX, &iPos);

    printf("[%d] @ position [%d]\n\n", iX, iPos);



    iX = -1;

    binarySearch(iList, iNum, iX, &iPos);

    printf("[%d] @ position [%d]\n\n", iX, iPos);



    iX = 35;

    binarySearch(iList, iNum, iX, &iPos);

    printf("[%d] @ position [%d]\n\n", iX, iPos);



    return 0;

}

编译

$ g++ -o binarySearch binarySearch.cpp

运行

$ ./binarySearch 

from [0] to [33]

from [0] to [15]

from [0] to [6]

from [4] to [6]

[5] @ position [5]



from [0] to [33]

from [0] to [15]

from [0] to [6]

from [4] to [6]

[6] @ position [-1]



from [0] to [33]

from [0] to [15]

from [0] to [6]

from [0] to [2]

[0] @ position [0]



from [0] to [33]

from [17] to [33]

from [26] to [33]

from [30] to [33]

from [32] to [33]

[33] @ position [32]



from [0] to [33]

from [0] to [15]

from [0] to [6]

from [0] to [2]

[-1] @ position [-1]



from [0] to [33]

from [17] to [33]

from [26] to [33]

from [30] to [33]

from [32] to [33]

[35] @ position [-1]

再见……