hdu4705 Y 2013 Multi-University Training Contest 10

Y

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 131072/131072 K (Java/Others) Total Submission(s): 304 Accepted Submission(s): 104

Problem Description

Sample Input

4

1 2

1 3

1 4

Sample Output

1
Hint

1. The only set is {2,3,4}.

2. Please use #pragma comment(linker, "/STACK:16777216")

一定要构个无向图，不构无向图会有神数据卡你:

 1 #pragma comment(linker, "/STACK:16777216")
 2 #include <iostream>
 3 #include <stdio.h>
 4 #include <stdlib.h>
 5 #include <algorithm>
 6 #include <math.h>
 7 #include <string.h>
 8 #include <set>
 9 #include <vector>
10 #define ll long long int
11 using namespace std;
12 vector<int> a[100005];
13 int b[100005];
14 ll sum,n;
15 ll x[100005];
16 int fun(int x1)
17 {
18     b[x1]=1;
19     int size=a[x1].size();
20      x[x1]=1;
21     int i;
22     for(i=0;i<size;i++)
23     if(!b[a[x1][i]])
24     x[x1]+=fun(a[x1][i]);
25     return x[x1];
26 }
27 void dfs(int x1)
28 {
29     b[x1]=1;
30     int size=a[x1].size();
31     if(size==0) return ;
32     int i;
33     ll ma=n-1;
34     for(i=0;i<size;i++)
35     if(!b[a[x1][i]])
36     {
37        ma-=x[a[x1][i]];
38     }
39     for(i=0;i<size;i++)
40     if(!b[a[x1][i]])
41     sum-=ma*x[a[x1][i]],ma+=x[a[x1][i]],dfs(a[x1][i]);
42 }
43 int main()
44 {
45     ll x1,y1;
46     int i,j;
47     while(scanf("%d",&n)!=EOF)
48     {
49         memset(x,0,sizeof(x));
50         sum=n*(n-1)/2*(n-2)/3;
51         memset(b,0,sizeof(b));
52         for(i=1;i<=n;i++)
53         a[i].clear();
54         for(i=1;i<n;i++)
55         {
56             scanf("%d%d",&x1,&y1);
57             a[x1].push_back(y1);
58             a[y1].push_back(x1);
59         }
60         fun(1);
61         memset(b,0,sizeof(b));
62         dfs(1);
63         cout<<sum<<endl;
64     }
65 }

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posted on 2013-08-23 00:37 ERKE 阅读(309) 评论(0) 收藏举报