hdu3081 Marriage Match II
新年第一篇,又花了一早上,真是蠢啊!
二分+网络流
之前对于讨论哪些人是朋友的时候复杂度过高
直接n3的暴力虽然看起来复杂度高,其实并不是每次都成立
#include<bits/stdc++.h>
using namespace std;
const int N = 205;
const int INF = 0x3f3f3f3f;
#define sz(X) ((int)X.size())
int A[N], B[N];
int mp[N][N];
int f[N];
int find(int x) { return f[x] == x? x : f[x] = find(f[x]); }
/***********Dinic*********/
int s, t;
struct Edge {
int from, to, cap, flow, nx;
Edge(int a=0, int b=0, int c=0, int d=0, int e=0):from(a), to(b), cap(c), flow(d),nx(e){}
}E[N*N];
int head[N], tot;
bool vis[N];
int d[N];
int cur[N];
void init() {
tot = 0; memset(head,-1,sizeof(head));
}
void add(int from, int to, int cap) {
E[tot] = Edge(from,to,cap,0,head[from]); head[from] = tot++;
E[tot] = Edge(to,from,0,0,head[to]); head[to] = tot++;
}
bool bfs() {
memset(vis, 0, sizeof(vis));
queue<int> Q;
Q.push(s);
d[s] = 0;
vis[s] = 1;
while(!Q.empty()) {
int x = Q.front(); Q.pop();
for(int i = head[x]; ~i; i = E[i].nx) {
Edge& e = E[i];
if(!vis[e.to] && e.cap > e.flow) {
vis[e.to] = 1;
d[e.to] = d[x] + 1;
Q.push(e.to);
}
}
}
return vis[t];
}
int dfs(int x, int a) {
if(x == t || a == 0) return a;
int flow = 0, f;
for(int& i = cur[x]; ~i; i = E[i].nx) {
Edge& e = E[i];
if(d[x]+1 == d[e.to] && (f = dfs(e.to, min(a, e.cap-e.flow))) > 0) {
e.flow += f;
E[i^1].flow -= f;
flow += f;
a -= f; if(a == 0) break;
}
}
return flow;
}
int Maxflow(int start, int ed) {
s = start; t = ed;
int flow = 0;
while(bfs()) {
for(int i = s; i <= t; ++i) cur[i] = head[i];
flow += dfs(s, INF);
}
return flow;
}
int main() {
int n,m,l;
int _; scanf("%d",&_);
while(_--) {
memset(mp,0,sizeof(mp));
scanf("%d %d %d",&n,&m,&l);
for(int i = 0; i <= n; ++i) f[i] = i;
for(int i = 0; i < m; ++i) {
int a, b; scanf("%d %d",&a,&b);
mp[a][b] = 1;
}
for(int i = 0; i < l; ++i) {
int c,d; scanf("%d %d",&c,&d);
int t1 = find(c); int t2 = find(d);
if(t1 != t2) f[t1] = t2;
}
for(int i = 1; i <= n; ++i) {
for(int j = 1; j <= n; ++j) {
if(find(i) == find(j)) {
for(int k = 1; k <= n; ++k) {
if(mp[i][k]) mp[j][k] = 1;
}
}
}
}
int s = 0; int t = 2*n+1;
int l = 0; int r = n; int res;
while(l <= r) {
int mid = (l + r)>>1;
init();
for(int i = 1; i <= n; ++i) add(s,i,mid);
for(int i = 1; i <= n; ++i) add(i+n,t,mid);
for(int i = 1; i <= n; ++i)
for(int j = 1; j <= n; ++j) {
if(mp[i][j]) {
add(i,j+n, 1);
}
}
int tt = Maxflow(s, t);
if(tt != mid*n) r = mid-1;
else { l = mid+1; res = mid; }
}
printf("%d\n",res);
}
return 0;
}