Pashmak and Graph（dp + 贪心）

题目链接：http://codeforces.com/contest/459/problem/E

题意：给一个带权有向图， 找出其中最长上升路的长度。

题解：先按权值对所有边排序， 然后依次 u ->v 权值w  则  f[u] = f[v] + 1; 这里需要注意的是 存在多条边权值相同， 这是应多条边一同计算。

 /***Good Luck***/
 #define _CRT_SECURE_NO_WARNINGS
 #include <iostream>
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
 #include <string>
 #include <algorithm>
 #include <stack>
 #include <map>
 #include <queue>
 #include <vector>
 #include <set>
 #include <functional>
 #include <cmath>

 #define Zero(a) memset(a, 0, sizeof(a))
 #define Neg(a)  memset(a, -1, sizeof(a))
 #define All(a) a.begin(), a.end()
 #define PB push_back
 #define inf 0x3f3f3f3f
 #define inf2 0x7fffffffffffffff
 #define ll long long
 using namespace std;
 //#pragma comment(linker, "/STACK:102400000,102400000")
 const int maxn = ;
 int dp[maxn], dp2[maxn];
 int rec[maxn];
 int n, e;
 struct node {
     int u, v;
     int w;
 }edge[maxn];

 bool cmp(node a, node b) {
     return a.w < b.w;
 }
 int main() {
     //freopen("data.out", "w", stdout);
     //freopen("data.in", "r", stdin);
     //cin.sync_with_stdio(false);
     scanf("%d%d", &n, &e);
     int u, v, w;
     for (int i = ; i < e; ++i) {
         scanf("%d%d%d", &u, &v, &w);
         edge[i].u = u;
         edge[i].v = v;
         edge[i].w = w;
     }
     sort(edge, edge + e, cmp);
     int j;
     for (int i = ; i < e; ++i) {
         for (j = i; j < e && edge[j].w == edge[i].w; ++j);

         for (int k = i; k < j; ++k) {
             dp2[edge[k].v] = max(dp2[edge[k].v], dp[edge[k].u] + );
         }
         for (int k = i; k < j; ++k) {
             dp[edge[k].v] = dp2[edge[k].v];
         }
         i = j - ;
     }
     int ans = ;
     for (int i = ; i <= n; ++i) {
         ans = max(ans, dp[i]);
     }
     cout << ans << endl;
     return ;
 }