Control HDU - 4289

https://cn.vjudge.net/problem/HDU-4289 

#include <iostream>
#include <cstring>
#include <queue>
#include <vector>
#include <algorithm>
#include <cstdio>
#include <set>
#include <map>
#include <cmath>
//#include<bits/stdc++.h>
using namespace std;

#define sfi(i) scanf("%d",&i)
#define sfl(i) scanf("%I64d",&i)
#define sfs(i) scanf("%s",(i))
#define pri(i) printf("%d\n",i)
#define sff(i) scanf("%lf",&i)
#define ll long long
#define ull unsigned long long
#define mem(x,y) memset(x,y,sizeof(x))
#define INF 0x3f3f3f3f
#define eps 1e-10
#define PI acos(-1.0)
#define lowbit(x) ((x)&(-x))
#define fl() printf("flag\n")
#define MOD(x) ((x%mod)+mod)%mod
#define endl '\n'
#define pb push_back
#define lson (rt<<1)
#define rson (rt<<1|1)
#define FAST_IO ios::sync_with_stdio(false);cin.tie(0);cout.tie(0)

const int maxn=1e4+9;
const int maxm=1e5+9;

struct E
{
    int to,nex,cap,flow;
}edge[maxm];
int head[maxn];
int tot;
int gap[maxn],dep[maxn],cur[maxn];
void init()
{
    tot=0;
    mem(head,-1);
}
void addedge(int u,int v,int w,int rw=0)
{
    edge[tot].to=v;
    edge[tot].cap=w;
    edge[tot].flow=0;
    edge[tot].nex=head[u];
    head[u]=tot++;

    edge[tot].to=u;
    edge[tot].cap=rw;
    edge[tot].flow=0;
    edge[tot].nex=head[v];
    head[v]=tot++;
}
int Q[maxn];
void bfs(int st,int ed)
{
    mem(dep,-1);
    mem(gap,0);
    gap[0]=1;
    int fr=0,re=0;
    dep[ed]=0;
    Q[re++]=ed;
    while(fr!=re)
    {
        int u=Q[fr++];
        for(int i=head[u];i!=-1;i=edge[i].nex)
        {
            int v=edge[i].to;
            if(dep[v]!=-1) continue;
            Q[re++]=v;
            dep[v]=dep[u]+1;
            gap[dep[v]]++;
        }
    }
}
int S[maxn];
int sap(int st,int ed,int n)
{
    bfs(st,ed);
    memcpy(cur,head,sizeof(head));
    int top=0;
    int u=st;
    int ans=0;
    while(dep[st]<n)
    {
        if(u==ed)
        {
            int Min=INF;
            int inser;
            for(int i=0;i<top;i++)
            {
                if(Min>edge[S[i]].cap-edge[S[i]].flow)
                {
                    Min=edge[S[i]].cap-edge[S[i]].flow;
                    inser=i;
                }
            }
            for(int i=0;i<top;i++)
            {
                edge[S[i]].flow+=Min;
                edge[S[i]^1].flow-=Min;
            }
            ans+=Min;
            top=inser;
            u=edge[S[top]^1].to;
            continue;
        }
        bool flag=false;
        int v;
        for(int i=cur[u];i!=-1;i=edge[i].nex)
        {
            v=edge[i].to;
            if(edge[i].cap-edge[i].flow&&dep[v]+1==dep[u])
            {
                flag=true;
                cur[u]=i;
                break;
            }
        }
        if(flag)
        {
            S[top++]=cur[u];
            u=v;
            continue;
        }
        int Min=n;
        for(int i=head[u];i!=-1;i=edge[i].nex)
        {
            if(edge[i].cap-edge[i].flow&&dep[edge[i].to]<Min)
            {
                Min=dep[edge[i].to];
                cur[u]=i;
            }
        }
        gap[dep[u]]--;
        if(!gap[dep[u]]) return ans;
        dep[u]=Min+1;
        gap[dep[u]]++;
        if(u!=st) u=edge[S[--top]^1].to;
    }
    return ans;
}

int n,m,s,t;
int w[maxn];
int main()
{
    FAST_IO;
    //freopen("input.txt","r",stdin);

    while(cin>>n>>m)
    {
        init();
        cin>>s>>t;
        for(int i=1;i<=n;i++)
        {
            cin>>w[i];
            addedge(i,i+n,w[i]);
            //addedge(i+n,i,w[i]);
        }
        for(int i=0;i<m;i++)
        {
            int u,v;
            cin>>u>>v;
            addedge(u+n,v,INF);
            addedge(v+n,u,INF);
        }
        t=t+n;
        int ans=sap(s,t,2*n);
        cout<<ans<<endl;
    }




    return 0;
}

 

#include <iostream>
#include <cstring>
#include <queue>
#include <vector>
#include <algorithm>
#include <cstdio>
#include <set>
#include <map>
#include <cmath>
//#include<bits/stdc++.h>
using namespace std;

#define sfi(i) scanf("%d",&i)
#define sfl(i) scanf("%I64d",&i)
#define sfs(i) scanf("%s",(i))
#define pri(i) printf("%d\n",i)
#define sff(i) scanf("%lf",&i)
#define ll long long
#define ull unsigned long long
#define mem(x,y) memset(x,y,sizeof(x))
#define INF 0x3f3f3f3f
#define eps 1e-10
#define PI acos(-1.0)
#define lowbit(x) ((x)&(-x))
#define fl() printf("flag\n")
#define MOD(x) ((x%mod)+mod)%mod
#define endl '\n'
#define pb push_back
#define lson (rt<<1)
#define rson (rt<<1|1)
#define FAST_IO ios::sync_with_stdio(false);cin.tie(0);cout.tie(0)

const int N=1e4+9;
const int M=4e4+9;

int head[N],tot,dist[N],cur[N];
int s,t;
int n,m;
int w[N];
struct Edge
{
   int from,to,next,flow,cap;

}edge[N*10];

void addedge(int a,int b,int c)
{
   edge[tot].from = a;edge[tot].to = b;edge[tot].cap = c;edge[tot].flow = 0;edge[tot].next = head[a];head[a] = tot++;
   edge[tot].from = b;edge[tot].to = a;edge[tot].cap = 0;edge[tot].flow = 0;edge[tot].next = head[b];head[b] = tot++;
}

bool BFS()
{
    memset(dist,0,sizeof(dist));
    dist[s] = 1;
    queue<int> que;
    que.push(s);
    while(!que.empty())
    {
        int u = que.front();
        que.pop();
        for(int i = head[u];~i;i = edge[i].next)
        {
            int to = edge[i].to;
            if(!dist[to]&&edge[i].cap > edge[i].flow)
            {
                dist[to] = dist[u] + 1;
                 que.push(to);
            }
        }
   }
   if(!dist[t])return false;
   return true;
}

int DFS(int pos,int MinFlow)
{
    if(pos==t||MinFlow==0)return MinFlow;
    int flow = 0;
    for(int &i = cur[pos];~i;i = edge[i].next)
    {
        int to = edge[i].to;
        if(dist[to]==dist[pos]+1&&edge[i].cap > edge[i].flow){
            int res = DFS(edge[i].to,min(MinFlow,edge[i].cap-edge[i].flow));
            edge[i].flow+=res;
            edge[i^1].flow-=res;
            flow+=res;
            MinFlow-=res;
            if(MinFlow==0)break;
        }
    }
    return flow;
}
int Dinic(int st,int et)
{
    if(st==et)return 0;
    int MaxFlow = 0;
    while(BFS())
    {
        memcpy(cur,head,sizeof(head));
        int ans = DFS(st,INF);
        MaxFlow+=ans;
    }
    return MaxFlow;
}

void init()
{
    tot=0;
    mem(head,-1);
}

int main()
{
    //FAST_IO;
    //freopen("input.txt","r",stdin);

    while(cin>>n>>m)
    {
        init();
        cin>>s>>t;
        for(int i=1;i<=n;i++)
        {
            cin>>w[i];
            addedge(i,i+n,w[i]);
            //addedge(i+n,i,w[i]);
        }
        for(int i=0;i<m;i++)
        {
            int u,v;
            cin>>u>>v;
            addedge(u+n,v,INF);
            addedge(v+n,u,INF);
        }
        t=t+n;
        int ans=Dinic(s,t);
        cout<<ans<<endl;
    }




    return 0;
}