Codeforces Round 261 Div.2 E Pashmak and Graph --DAG上的DP

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
using namespace std;
#define N 100007

struct node
{
    int u,v,w;
}edge[3*N];
int dp[3*N],dis[3*N];

int cmp(node ka,node kb)
{
    return ka.w < kb.w;
}

int main()
{
    int n,m,i,j;
    scanf("%d%d",&n,&m);
    for(i=0;i<m;i++)
        scanf("%d%d%d",&edge[i].u,&edge[i].v,&edge[i].w);
    memset(dp,0,sizeof(dp));
    memset(dis,0,sizeof(dis));
    sort(edge,edge+m,cmp);
    edge[m].w = -1;
    int ans = 1;
    int maxi = 1;
    for(i=m-1;i>=0;i--)
    {
        int u = edge[i].u;
        int v = edge[i].v;
        int w = edge[i].w;
        maxi = dp[v]+1;
        dis[u] = max(dis[u],max(maxi,dp[u]));
        ans = max(ans,maxi);
        if(i == 0 || w > edge[i-1].w)
        {
            for(j=i;j<m;j++)   //更新相同边权的dp值
            {
                dp[edge[j].u] = dis[edge[j].u];
                if(edge[j].w != edge[j+1].w)
                    break;
            }
        }
    }
    printf("%d\n",ans);
    return 0;
}