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 = 300005;
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 = 0; 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 = 0; 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] + 1);
        }
        for (int k = i; k < j; ++k) {
            dp[edge[k].v] = dp2[edge[k].v];
        }
        i = j - 1;
    }
    int ans = 0;
    for (int i = 1; i <= n; ++i) {
        ans = max(ans, dp[i]);
    }
    cout << ans << endl;
    return 0;
}