p3163 [CQOI2014]危桥

传送门

分析

代码

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<algorithm>
#include<cctype>
#include<cmath>
#include<cstdlib>
#include<queue>
#include<ctime>
#include<vector>
#include<set>
#include<map>
#include<stack>
using namespace std;
#define wh ((i&1)?1:-1)
const int inf = 1e9+;
int g[][],s,t,n,to[],head[],w[],nxt[];
int level[],cur[],cnt,ano[];
inline void init(){
    memset(head,,sizeof(head));
    cnt=;
}
inline void add(int x,int y,int z){
    nxt[++cnt]=head[x];
    head[x]=cnt;
    to[cnt]=y;
    w[cnt]=z;
    nxt[++cnt]=head[y];
    head[y]=cnt;
    to[cnt]=x;
    w[cnt]=z;
    ano[cnt]=cnt-;
    ano[cnt-]=cnt;
}
inline void deal(){
    int i,j,k;
    for(i=;i<n;i++)
      for(j=i+;j<=n;j++)
        if(g[i][j]==)add(i,j,);
          else if(g[i][j]==)add(i,j,inf);
}
inline bool bfs(){
    memset(level,-,sizeof(level));
    queue<int>q;
    q.push(s);
    level[s]=;
    while(!q.empty()){
      int x=q.front();
      q.pop();
      for(int i=head[x];i;i=nxt[i])
        if(w[i]&&level[to[i]]==-){
          level[to[i]]=level[x]+;
          if(to[i]==t)return ;
          q.push(to[i]);
        }
    }
    return ;
}
inline int dfs(int x,int flow){
    if(x==t)return flow;
    int res=;
    cur[x]=head[x];
    for(int i=cur[x];i;i=nxt[i]){
      cur[x]=i;
      int y=to[i];
      if(level[y]==level[x]+&&w[i]){
          int f=dfs(y,min(flow-res,w[i]));
          res+=f;
          w[i]-=f;
          w[ano[i]]+=f;
      }
    }
    if(!res)level[x]=-;
    return res;
}
int main(){
    int a1,a2,b1,b2,an,bn,i,j,k,Ans1,Ans2;
    while(~scanf("%d",&n)){
      scanf("%d%d%d%d%d%d",&a1,&a2,&an,&b1,&b2,&bn);
      a1++,a2++,b1++,b2++;
      for(i=;i<=n;i++){
          char s[];
        scanf("%s",s);
        for(j=;j<n;j++){
          if(s[j]=='O')g[i][j+]=;
            else if(s[j]=='N')g[i][j+]=;
            else g[i][j+]=;
        }
      }
      init();
      Ans1=;
      deal();
      s=n+,t=n+;
      add(s,a1,an<<),add(s,b1,bn<<);
      add(a2,t,an<<),add(b2,t,bn<<);
      while(bfs())while(int a=dfs(s,inf))Ans1+=a;
      init();
      Ans2=;
      deal();
      s=n+,t=n+;
      add(s,a1,an<<),add(s,b2,bn<<);
      add(a2,t,an<<),add(b1,t,bn<<);
      while(bfs())while(int a=dfs(s,inf))Ans2+=a;
      if(Ans1!=(an<<)+(bn<<)||Ans2!=(an<<)+(bn<<))puts("No");
        else puts("Yes");
    }
    return ;
}