Time Limit: 10000/5000 MS (Java/Others) Memory Limit: 65536/65536 K (Java/Others)
Total Submission(s): 1654 Accepted Submission(s): 429
/*
hdu 5739 割点
problem:
给你一个无向图,G[i]为删除i点时,无向图的价值. 求 sum(i*G[i])%mod
如果当前是连通的,那么连通分量的价值为所有点权值的积(任意两个节点连通)
否则为拆分后的各个连通分量的价值的和
solve:
所以需要判断当前点是否是割点.
如果不是割点,只需要减去这个点的权值即可. 如果是割点,要减去这个连通分量的价值再加上拆散后的各个连通分量的值
最开始题意理解错了- -,而且模板有点问题,一直wa.
hhh-2016-08-27 19:47:17
*/
#pragma comment(linker,"/STACK:124000000,124000000")
#include <algorithm>
#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <cstring>
#include <vector>
#include <math.h>
#include <queue>
#include <map>
#define lson i<<1
#define rson i<<1|1
#define ll long long
#define clr(a,b) memset(a,b,sizeof(a))
#define scanfi(a) scanf("%d",&a)
#define scanfl(a) scanf("%I64d",&a)
#define key_val ch[ch[root][1]][0]
#define inf 1e9
using namespace std;
const ll mod = 1e9+7;
const int maxn = 100005;
struct Edge
{
bool cut ;
int v,next,w;
} edge[maxn*5];
int head[maxn],tot;
int low[maxn],dfn[maxn],Stack[maxn],index,top;
bool Instack[maxn],cut[maxn];
int bridge;
ll val[maxn],mul[maxn],ans[maxn],fans[maxn],tval[maxn];
void add_edge(int u,int v)
{
edge[tot].v = v,edge[tot].next = head[u],head[u] = tot++;
}
ll tans =1 ;
ll pow_mod(ll a,ll n)
{
ll cnt =1 ;
while(n)
{
if(n & 1) cnt = cnt*a%mod;
a = a*a%mod;
n >>= 1;
}
return cnt ;
}
int now;
vector<int> vec[maxn];
int from[maxn];
void Tarjan(int u,int ance,int pre)
{
int v;
vec[now].push_back(u);
from[u] = now;
low[u] = dfn[u] = ++index;
Stack[top++] = u;
Instack[u] = true;
tans = tans*val[u] % mod;
int son = 0;
for(int i= head[u]; i!= -1; i = edge[i].next)
{
v = edge[i].v;
if(v == pre){
continue;
}
if(!dfn[v])
{
son ++ ;
ll tp = tans;
Tarjan(v,ance,u);
low[u] = min(low[u],low[v]);
if(u != pre && low[v] >= dfn[u])
{
cut[u] = true;
ll ta = tans * pow_mod(tp,mod-2)%mod;
// cout <<"node:" << u <<" ta:" <<ta <<endl;
ans[u] = (ans[u] + ta)%mod;
fans[u] = (fans[u] * ta) % mod;
}
}
else if(low[u] > dfn[v])
low[u] = dfn[v];
}
if(u == ance && son > 1)
cut[u] = true;
Instack[u] = false;
top --;
}
void init(int n)
{
for(int i = 0; i <= n+1; i++)
{
head[i] = -1;
ans[i] = 0;
fans[i] = 1;
Instack[i]=cut[i]= 0;
dfn[i] = 0;
vec[i].clear();
}
tot=top=index=0;
}
int main()
{
// freopen("in.txt","r",stdin);
int T,n,m,u,v;
scanfi(T);
while(T--)
{
scanfi(n),scanfi(m);
init(n);
for(int i =1; i <= n; i++)
{
scanfl(val[i]);
fans[i] = 1;
}
for(int i = 0; i < m; i++)
{
scanfi(u),scanfi(v);
add_edge(u,v);
add_edge(v,u);
}
now = 1;
ll ob = 0;
for(int i = 1; i <= n; i++)
{
if(!dfn[i])
{
tans= 1;
Tarjan(i,i,-1);
tval[now] = tans;
ll amul = tans;
ob = (ob+tans) %mod;
// cout << "all:" <<tans<<endl;
for(int j = 0 ; j < vec[now].size(); j ++)
{
int to = vec[now][j];
// cout << to <<" " << fans[to] << endl;
if(to == i) continue;
ans[to] = (ans[to] + amul*pow_mod(fans[to]*val[to]%mod,mod-2)%mod);
if(ans[to] > mod) ans[to] -= mod;
}
now ++;
}
}
ll out = 0;
ll tm;
for(int i = 1; i <= n; i++)
{
// cout << fans[i] <<" " << ans[i] <<" " <<cut[i] << endl;
int tf = from[i];
if(cut[i])
{
tm = (ob - tval[tf] + ans[i] + mod)%mod;
}
else
{
if(vec[from[i]].size() > 1)
tm = (ob - tval[tf] + tval[tf]*pow_mod(val[i],mod-2)%mod + mod) % mod;
else
tm = (ob - tval[tf] + mod) % mod;
}
out = (out + i * tm % mod) % mod;
}
printf("%I64d\n",out);
}
return 0;
}
/*
3
4 3
1 2 3 4
1 2
2 3
1 3
4 2
100000000 131231232 312354435 432134234
1 2
3 4
66
315142079
*/
原文:http://www.cnblogs.com/Przz/p/5813676.html