Codeforces 459E Pashmak and Graph

http://www.codeforces.com/problemset/problem/459/E

题意:

给出n个点,m条边的有向图，每个边有边权，求一条最长的边权上升的路径的长度。

思路:用f存边，g存点，然后排序转移，注意相同的要延迟转移

#include<cstdio>
#include<cmath>
#include<algorithm>
#include<cstring>
#include<iostream>
struct edge{
    int u,v,w;
}e[300005];
int n,m,f[300005],g[300005];
int read(){
    int t=0,f=1;char ch=getchar();
    while (ch<'0'||ch>'9'){if (ch=='-') f=-1;ch=getchar();}
    while ('0'<=ch&&ch<='9'){t=t*10+ch-'0';ch=getchar();}
    return t*f;
}
bool cmp(edge a,edge b){
    return a.w<b.w;
}
int main(){
    n=read();m=read();
    for (int i=1;i<=m;i++){
        e[i].u=read();e[i].v=read();e[i].w=read();
    }
    std::sort(e+1,e+1+m,cmp);
    int t=1,ans=0;
    for (int i=1;i<=m;i++){
        f[i]=g[e[i].u]+1;
        if (e[i].w!=e[i+1].w){
            for (int j=t;j<=i;j++)
             g[e[j].v]=std::max(g[e[j].v],f[j]);
            t=i+1; 
        }
        ans=std::max(ans,f[i]);
    }
    printf("%d\n",ans);
    return 0;
}