hdu 3549 Flow Problem 增广路ford-fullkerson算法

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#include<stdio.h>#include<string.h>#include<queue>#include<vector>#include<algorithm>using namespace std;const int N=1024*2;const int inf=1<<24;struct arc{    int c,f;} g[N][N];int n,m,i,j,u,v,c,f;int abs(int x){    if(x<0) return -x;    else return x;}void ford(){    int p[N],a[N],flag[N];    queue<int>q;    while(1)    {        memset(p,0xff,sizeof(p));        memset(a,0xff,sizeof(a));        memset(flag,0xff,sizeof(flag));        while(!q.empty()) q.pop();        q.push(0);        flag[0]=0;        p[0]=0;        a[0]=inf;        while(!q.empty()&&flag[n-1]==-1)        {            u=q.front();            q.pop();            for(i=0; i<n; i++)            {                if(flag[i]==-1)                {                    if(g[u][i].c<inf&&g[u][i].f<g[u][i].c)                    {                        flag[i]=0;                        p[i]=u;                        a[i]=min(a[u],g[u][i].c-g[u][i].f);                        q.push(i);                    }                    else if(g[i][u].c<inf&&g[i][u].f>0)                    {                        flag[i]=0;                        p[i]=-u;                        a[i]=min(a[u],g[i][u].f);                        q.push(i);                    }                }            }            flag[u]=1;        }        //printf("%d %d\n",flag[n-1],a[n-1]);        if(flag[n-1]==-1||a[n-1]==0) break;        int k1=n-1,k2=abs(p[k1]);        int add=a[n-1];        while(1)        {            if(g[k2][k1].f<inf)                g[k2][k1].f+=add;            else                g[k1][k2].f-=add;            if(k2==0) break;            k1=k2;            k2=abs(p[k2]);        }    }    int flow=0;    for(i=0; i<n; i++)        if(g[0][i].f<inf)            flow+=g[0][i].f;    printf("%d\n",flow);}int main(){    int _;    scanf("%d",&_);    for(int k=1; k<=_; k++)    {        scanf("%d%d",&n,&m);        for(i=0; i<n; i++)            for(j=0; j<n; j++)                g[i][j].c=g[i][j].f=inf;        for(i=0; i<m; i++)        {            scanf("%d%d%d",&u,&v,&c);            u--;            v--;            if(g[u][v].c==inf)                g[u][v].c=c;            else                g[u][v].c+=c;            g[u][v].f=0;        }        printf("Case %d: ",k);        ford();    }    return 0;}
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