[SPOJ FASTFLOW] Fast Maximum Flow [最大流]

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最大流模板题

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dinic 4.5秒...

//dinic#include <cstdio>#include <cstring>using namespace std;const long long MAXINT=(1ll<<60);const int N=5010;const int M=30010;struct NetWorkFlow {struct Node {int fe,h,cur;long long v;};struct Edge {int t,ne;long long f;};Node a[N];Edge b[M*2];int d[M];int s,t,n,p;void clear(int nn,int ss,int tt) {n=nn;s=ss;t=tt;for (int i=0;i<=n;i++) {a[i].fe=-1;a[i].v=0;}p=0;}void putedge(int x,int y,long long f) {b[p].t=y;b[p].f=f;b[p].ne=a[x].fe;a[x].fe=p;p++;b[p].t=x;b[p].f=f;b[p].ne=a[y].fe;a[y].fe=p;p++;}bool bfs() {int i,p,q,j;for (i=0;i<=n;i++) a[i].h=0;a[s].h=1;p=q=0;d[q++]=s;while (p<q) {i=d[p];for (j=a[i].fe;j!=-1;j=b[j].ne) {if (a[b[j].t].h==0&&b[j].f>0) {a[b[j].t].h=a[i].h+1;if (b[j].t==t) return true;d[q++]=b[j].t;}}p++;}return false;}long long dfs(int i,long long v) {if (i==t) {a[t].v+=v;return v;}int j;long long ans=0,x;for (j=a[i].cur;j!=-1&&v>0;j=b[j].ne) {if (b[j].f>0&&a[b[j].t].h>a[i].h) {if (b[j].f<v) x=dfs(b[j].t,b[j].f);else x=dfs(b[j].t,v);v-=x;b[j].f-=x;b[j^1].f+=x;ans+=x;}}a[i].cur=j;a[i].v+=ans;return ans;}long long flow() {int i;a[s].v=MAXINT;while (bfs()) {for (i=0;i<=n;i++) a[i].cur=a[i].fe;dfs(s,MAXINT);}return a[t].v;}};NetWorkFlow c;int n,m;int main() {int i,x,y,z;scanf("%d%d",&n,&m);c.clear(n,1,n);for (i=0;i<m;i++) {scanf("%d%d%d",&x,&y,&z);c.putedge(x,y,z);}printf("%lld\n",c.flow());return 0;}

//isap#include <cstdio>#include <cstring>using namespace std;const long long MAXINT=(1ll<<60);const int N=5010;const int M=30010;struct NetWorkFlow {struct Edge {int t;long long f;Edge *ne,*p;Edge () {}Edge (int tt,int ff,Edge *nee) {t=tt;f=ff;ne=nee;}void *operator new(size_t,void *p) {return p;}};Edge b[M*2];Edge *p,*fe[N],*cur[N];int n,s,t;int h[N],vh[N];void clear(int nn,int ss,int tt) {n=nn;s=ss;t=tt;for (int i=0;i<=n;i++) fe[i]=NULL;p=b;}void putedge(int x,int y,int f) {fe[x]=new(p++)Edge(y,f,fe[x]);fe[y]=new(p++)Edge(x,f,fe[y]);fe[x]->p=fe[y];fe[y]->p=fe[x];}long long aug(int i,long long f) {if (i==t) return f;long long l=f;for (Edge *&j=cur[i];j;j=j->ne) {if (j->f&&h[j->t]+1==h[i]) {long long tmp=aug(j->t,l<j->f?l:j->f);j->f-=tmp;j->p->f+=tmp;l-=tmp;if (h[s]==n||!l) return f-l;}}int minh=n-1;for (Edge *j=cur[i]=fe[i];j;j=j->ne) {if (j->f&&h[j->t]<minh) minh=h[j->t];}minh++;if (!--vh[h[i]]) h[s]=n;else ++vh[h[i]=minh];return f-l;}long long flow() {long long ans=0;vh[0]=n;for (int i=0;i<=n;i++) {cur[i]=fe[i];h[i]=vh[i]=0;}while (h[s]<n) ans+=aug(s,MAXINT);return ans;}};NetWorkFlow c;int n,m;int main() {int i,x,y,z;scanf("%d%d",&n,&m);c.clear(n,1,n);for (i=0;i<m;i++) {scanf("%d%d%d",&x,&y,&z);c.putedge(x,y,z);}printf("%lld\n",c.flow());return 0;}

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