10474 - Where is the Marble?

排序，检索；

使用 bsearch 的 cmp 不能只返回 -1 或 1 （可能是要用差进行比较）；

# include <stdio.h>

# include <stdlib.h>

# include <string.h>



# define N 10005



int n, q, a[N], f[N];



int cmp(const void *x, const void *y){return ( *(int*)x - *(int*)y );}



int main()

{

    int i, cnt, x;

        

    cnt = 0;

    while (1)

    {

        scanf("%d%d", &n, &q);

        if (!n && !q) break;

        

        ++cnt;

        printf("CASE# %d:\n", cnt);

        for (i = 0; i < n; ++i) scanf("%d", &a[i]);

        

        qsort(a, n, sizeof(a[0]), cmp);

        

        memset(f, 0, sizeof(f));

        for (i = 0; i < n; ++i) if (!f[a[i]]) f[a[i]] = i+1;

        for (i = 0; i < q; ++i)    

        {

            scanf("%d", &x);

            if (!f[x]) printf("%d not found\n", x);

            else printf("%d found at %d\n", x, f[x]);

        }

    }

    

    return 0;

}

使用 bsearch ：

View Code

# include <stdio.h>

# include <stdlib.h>



# define N 10005



int n, q, f[N], h[N];



int cmp(const void *x, const void *y) {return *(int*)x - *(int*)y;}



int main()

{

    int i, x, *p, cnt;

        

    cnt = 0;

    while (1)

    {

        scanf("%d%d", &n, &q);

        if (!n && !q) break;

        

        ++cnt;

        printf("CASE# %d:\n", cnt);

        for (i = 0; i < n; ++i) scanf("%d", &f[i]);

        

        qsort(f, n, sizeof(f[0]), cmp);

        

        for (i = 0; i < q; ++i)

        {

            scanf("%d", &x);

            p = (int*)bsearch(&x, f, n, sizeof(f[0]), cmp);

            if (p == NULL) printf("%d not found\n", x);

            else

            {

                while (*(--p) == x) ;

                printf("%d found at %d\n", x, p-f+2);

            }

        }

    }

    

    return 0;

}