一道题目(intel?)

  从序列中找四个四字子串形成十进制数使之乘积最大(就是求四个最大的?),我目前只想到如下办法。这个题并不是关于复杂的算法,其本意是要利用并行处理,但目前尚未考虑到(除了其中比较求最小值部分有希望用SIMD)。

#include <stdio.h>

int g_TestString[] = {
   8,9,9,0,1,2,8,6,9,8,0,1,7,9,2,3,1,5,2,3,1,7,2,8,9,7,6,8,9,0,2,5,1,7,3,4,8,9,0,7,3,1,2
};

int main (void)
{
    int i, j;
    int n = sizeof(g_TestString) / sizeof(int);
    int picked[4] = {0,0,0,0};
    int pickedFrom[4] = {-1,-1,-1,-1};
    int least = 99999;  /* big enough */
    int leastPos = 0;

    /* first fueling */
    int cur = 0;
    for (i = 0; i < 4; i++)
    {
        cur *= 10;
        cur += g_TestString[i];
    }
    for (i = 0; i < 4; i++)
    {
        picked[i] = cur;
        pickedFrom[i] = i;

        if (cur < least)
        {
            least = cur;
            leastPos = i;
        }

        cur -= g_TestString[i] * 1000;
        cur *= 10;
        cur += g_TestString[i + 4];
    }

    for (i = 4; i < n - 4; i++)
    {
        if (least < cur)
        {
            int tempLeast, tempLeastPos;

            picked[leastPos] = cur;
            pickedFrom[leastPos] = i;

            /* refresh */
            if (picked[0] < picked[1])
            {
                tempLeast = picked[0];
                tempLeastPos = 0;
            }
            else
            {
                tempLeast = picked[1];
                tempLeastPos = 1;
            }

            if (picked[2] < picked[3])
            {
                least = picked[2];
                leastPos = 2;
            }
            else
            {
                least = picked[3];
                leastPos = 3;
            }

            if (tempLeast < least)
            {
                least = tempLeast;
                leastPos = tempLeastPos;
            }
        }

        cur -= g_TestString[i] * 1000;
        cur *= 10;
        cur += g_TestString[i + 4];

    }

    for (i = 0; i < 4; i++)
    {
        printf("%d picked from %d/n", picked[i], pickedFrom[i]);
    }

    return 0;
}

输出结果:
9231 picked from 13
9901 picked from 1
9768 picked from 24
9801 picked from 8

posted @ 2007-05-23 09:35  quanben  阅读(181)  评论(0编辑  收藏  举报