HDU 3549 Flow Problem

N is the given vertex, M is the edge, and the following m rows are each edge.

Idea: I am still using the ek algorithm. Now I only know this algorithm. I use C ++ for more than 4000 Ms. If you are interested, please do not use this algorithm! Below is a multi-channel augmented code, which can be used for reference, 78 Ms

My AC code:

#include<stdio.h>#include<string.h>#include<algorithm>#include<queue>using namespace std;#define INF 100000000#define N 1000int cap[N][N],flow[N][N];int p[N],a[N];int m,t;int Edmonds_Karp(int s){    int f=0;    queue<int >q;    while(1)    {        memset(a,0,sizeof(a));        a[s]=INF;        q.push(s);        while(!q.empty())        {            int u=q.front();            q.pop();            for(int v=1;v<=t;v++)            if(!a[v]&&cap[u][v]>flow[u][v])            {                p[v]=u;                q.push(v);                a[v]=min(a[u],cap[u][v]-flow[u][v]);            }        }        if(a[t]==0)break;        for(int u=t;u!=s;u=p[u])        {            flow[p[u]][u]+=a[t];            flow[u][p[u]]-=a[t];        }        f+=a[t];    }    return  f;}int main(){    int u,v,w,i,j,n,cnt=1;    scanf("%d",&n);    while(n--)    {        scanf("%d %d",&t,&m);        memset(cap,0,sizeof(cap));        memset(flow,0,sizeof(flow));        for(i=0;i<m;i++)        {            scanf("%d %d %d",&u,&v,&w);            cap[u][v]+=w;        }        printf("Case %d: %d\n",cnt++,Edmonds_Karp(1));    }    return 0;}

Multi-channel augmented:

#include <cstdio>#include <string.h>#include <algorithm>using namespace std;const int NMax=5000;struct edge{    int num,len;    edge *next,*rev;}*S[NMax],pool[NMax];int N,M,level[NMax],Q[NMax];bool makelevel(){    memset(level,-1,sizeof(level));    int tmp;    Q[0]=1;    level[1]=0;    for(int i=0,bot=1;i<bot;i++)    {        tmp=Q[i];        for(edge *p=S[tmp];p;p=p->next)            if(p->len>0 && level[p->num]==-1)                level[Q[bot++]=p->num]=level[tmp]+1;    }    return level[N]!=-1;}int DFS(int a,int alpha){    if(a==N) return alpha;    int tot=0,tmp;    for(edge *p=S[a];p && tot<alpha;p=p->next)    {        if(p->len>0 && level[p->num]==level[a]+1)        {            if(tmp=DFS(p->num,min(alpha-tot,p->len)))            {                tot+=tmp;                p->len-=tmp;                if(p->rev) p->rev->len+=tmp;            }        }    }    if(!tot) level[a]=-1;    return tot;}int main(){    int x,y,z,L,tmp;    int T;    scanf("%d",&T);    for(int I=1;I<=T;I++)    {        scanf("%d%d",&N,&M);        L=0;        memset(S,0,sizeof(S));        for(int i=1;i<=M;i++)        {            scanf("%d%d%d",&x,&y,&z);            edge *p=&pool[L++],*q=&pool[L++];            p->num=y; p->len=z; p->next=S[x];            q->num=x; q->len=0; q->next=S[y];            p->rev=q; q->rev=p;            S[x]=p; S[y]=q;        }        int ans=0;        while(makelevel())            while(tmp=DFS(1,(~0u>>1)))                ans+=tmp;        printf("Case %d: %d\n",I,ans);    }    getchar(); getchar();    return 0;}