poj 1201——Intervals

差分約束

建圖spfa求的最長路徑

 

#include<iostream>#include<cstdio>#include<queue>#include<cstring>using namespace std;#define INF 100000int head[151000],v[151000],w[151000],next[151000];int dis[51000];bool vis[51000];int cnt,n,m;void add(int a,int b,int c){v[cnt]=b;w[cnt]=c;next[cnt]=head[a];head[a]=cnt++;}void spfa(){memset(vis,0,sizeof(vis));for(int i=0;i<=n;i++)dis[i]=-INF;queue<int> q;dis[0]=0;q.push(0);while(!q.empty()){int u=q.front();q.pop();vis[u]=0;for(int i=head[u];i!=-1;i=next[i])if(dis[v[i]]<dis[u]+w[i]){dis[v[i]]=dis[u]+w[i];if(!vis[v[i]]){vis[v[i]]=1;q.push(v[i]);}}}printf("%d\n",dis[n]);}int main(){while(~scanf("%d",&m)){cnt=1;n=0;memset(head,-1,sizeof(head));for(int i=0;i<m;i++){int x,y,z;scanf("%d%d%d",&x,&y,&z);add(x-1,y,z);n=max(n,y);}for(int i=1;i<=n;i++){add(i-1,i,0);add(i,i-1,-1);}spfa();}return 0;}