拿不到比赛的第二名，我只能拿下冠军

Question

此代码尝试通过选择完成比赛时间较少的玩家来找到比赛的获胜者和第二名。

#include <stdio.h>

int main(void){
    int id[8] = {0};
    float time[8] = {0};
    for(size_t i=0; i<8; ++i) {
        printf("\nWrite id player: ");
        scanf("%d", &(id[i]));
        printf("\nWrite time: ");
        scanf("%f", &(time[i]));
    }
    size_t num1 = 0;
    size_t num2 = 0;
    for(size_t j=0; j<8; ++j){
        if (time[num1]>time[j]){
            num1 = j;       // to find the winner
        }
        if (time[num2]>time[j] && time[num2]>time[num1]){
            num2 = j;       // to find the second position player
        }
    }

    printf("\n\nWinner: %d, with time: %f", id[num1], time[num1]);
    printf("\n\nSecond: %d, with time: %f", id[num2], time[num2]);
    printf("\n\n");
}

不明白为什么这不起作用，它只适用于获胜者，但不适用于第二名。

输出：

Write id player: 1838

Write time: 4

Write id player: 3492

Write time: 6

Write id player: 3219 

Write time: 2

Write id player: 48929

Write time: 9

Write id player: 38928

Write time: 4

Write id player: 23892

Write time: 4

Write id player: 89498

Write time: 1

Write id player: 48929

Write time: 6


Winner: 89498, with time: 1.000000

Second: 89498, with time: 1.000000

time[num2]>time[j] && time[num2]>time[num1] 条件不应该完成这项工作吗？ &&不应该确保第二个获胜者的时间是第j次的次要，但也大于获胜者。

Answer 1

你的逻辑是错误的，你需要一个初始值来比较，一个工作的例子（用整数简化只是为了显示逻辑）：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main(void)
{
    srand((unsigned)time(NULL));

    int arr[8] = {0};

    for (size_t i = 0; i < 8; ++i)
    {
        arr[i] = rand() % 100;
        printf("%d\n", arr[i]);
    }
    puts("--");

    int num1 = 0;
    int num2 = 0;
    int time1 = 100;
    int time2 = 100;

    for (int i = 0; i < 8; ++i)
    {
        if (arr[i] < time1)
        {
            time1 = arr[i];
            num1 = i;
        }
        if ((arr[i] < time2) && (arr[i] > time1))
        {
            time2 = arr[i];
            num2 = i;
        }
    }
    printf("id: %d value %d\n", num1, arr[num1]);
    printf("id: %d value %d\n", num2, arr[num2]);
}

注意标准库可以在这种情况下提供帮助，qsort 是你的朋友，变量更少，代码更少，更不容易出错：

#include <stdio.h>
#include <stdlib.h>

typedef struct
{
    int id;
    float time;
} runner;

static int comp(const void *pa, const void *pb)
{
    const runner *a = pa;
    const runner *b = pb;

    return a->time < b->time ? -1 : a->time > b->time;
}

int main(void)
{
    runner runners[8] = {{0, .0f}};

    for (size_t i = 0; i < 8; ++i)
    {
        printf("\nWrite id player: ");
        scanf("%d", &runners[i].id);
        printf("\nWrite time: ");
        scanf("%f", &runners[i].time);
    }
    qsort(runners, 8, sizeof(runner), comp);
    printf("\n\nWinner: %d, with time: %f", runners[0].id, runners[0].time);
    printf("\n\nSecond: %d, with time: %f", runners[1].id, runners[1].time);
    printf("\n\n");
}