DAG最长路径

int dfs1(int s) {
    if(dis[s] > 0)return dis[s];
    for(int i = 0; i < G[s].size(); ++i) {
        int to = G[s][i];
        dis[s] = max(dis[s], dfs1(to) + w[s][to]);
    }
    return dis[s];
}

int dfs1(int s) {
    if(dis[s] > 0)return dis[s];
    for(int i = 0; i < G[s].size(); ++i) {
        int to = G[s][i];
        int tmp = dfs1(to) + w[s][to];
        if(dis[s] < tmp){
            dis[s] = tmp;
            next[s] = to;
        }
    }
    return dis[s];
}