BZOJ2435: [Noi2011]道路修建

这种水题真是……没一次AC都不好意思见人啊

P.S. LINUX无限栈真是爽炸了… 我爱递归

 1 /**************************************************************

 2     Problem: 2435

 3     User: zhuohan123

 4     Language: C++

 5     Result: Accepted

 6     Time:5320 ms

 7     Memory:93192 kb

 8 ****************************************************************/

 9  

10 #include <iostream>

11 #include <cstdio>

12 using namespace std;

13 inline int iabs(int a){return a<0?-a:a;}

14 inline int getnum()

15 {

16     int ans=0;char ch=getchar();

17     while(ch<'0'||ch>'9')ch=getchar();

18     while(ch>='0'&&ch<='9')ans=ans*10+ch-'0',ch=getchar();

19     return ans;

20 }

21 int n;

22 struct point{int head,f,size;}p[1100000];

23 struct edge{int next,to,c;}g[2100000];int gnum;

24 void addedge(int from,int to,int c)

25 {

26     g[++gnum].to=to;g[gnum].c=c;g[gnum].next=p[from].head;p[from].head=gnum;

27 }

28 long long ans=0;

29 void dfs(int po)

30 {

31     p[po].size++;

32     for(int i=p[po].head;i;i=g[i].next)

33         if(g[i].to!=p[po].f)

34         {

35             p[g[i].to].f=po;

36             dfs(g[i].to);

37             p[po].size+=p[g[i].to].size;

38             ans+=(long long)g[i].c*iabs(n-2*p[g[i].to].size);

39         }

40 }

41 int main(int argc, char *argv[])

42 {

43     n=getnum();

44     for(int i=1;i<n;i++)

45     {

46         int u=getnum(),v=getnum(),c=getnum();

47         addedge(u,v,c);addedge(v,u,c);

48     }

49     dfs(1);

50     cout<<ans<<endl;

51     return 0;

52 }