csu 1010 Water Drinking

并查集变种；

# include <stdio.h>
# include <memory.h>

# define MAXN 100005

int pre[MAXN];
int dis[MAXN];

int main()
{
    int n, x, y, i, mind, ans;

    while (~scanf("%d", &n))
    {
        memset(dis, 0, sizeof(dis));
        for (i = 0; i < MAXN; ++i)
            pre[i] = i;
        while (n--)
        {
            scanf("%d%d", &x, &y);
            pre[y] = x;
            dis[x] = 1;
        }
        for (mind = MAXN, ans = i = 0; i < MAXN; ++i)
            if (!dis[i])
            {
                x = i;
                while (pre[x] != x)
                {
                    x = pre[x];
                    ++dis[i];
                }
                if (!x  && dis[i] < mind)
                {
                    mind = dis[i];
                    ans = i;
                }
            }
        printf("%d\n", ans);
    }

    return 0;
}

下面的程序有一个特别严重的小错误。

View Code

 1 # include <stdio.h>
 2 # include <memory.h>
 3 
 4 # define MAXN 100005
 5 
 6 int pre[MAXN];
 7 int dis[MAXN];
 8 
 9 int main()
10 {
11     int n, x, y, i, maxn, mind, ans;
12 
13     while (~scanf("%d", &n))
14     {
15         memset(dis, 0, sizeof(dis));
16         for (i = 0; i < MAXN; ++i)
17             pre[i] = i;
18         while (n--)
19         {
20             scanf("%d%d", &x, &y);
21             pre[y] = x;
22             dis[x] = 1;
23             maxn = (x>y ? x:y);
24         }
25         for (mind = maxn+1, ans = i = 0; i <= maxn; ++i)
26             if (!dis[i])
27             {
28                 x = i;
29                 while (pre[x] != x)
30                 {
31                     x = pre[x];
32                     ++dis[i];
33                 }
34                 if (!x  && dis[i] < mind)
35                 {
36                     mind = dis[i];
37                     ans = i;
38                 }
39             }
40         printf("%d\n", ans);
41     }
42 
43     return 0;
44 }