2015 Multi-University Training Contest 3 hdu 5325 Crazy Bobo

Crazy Bobo

Time Limit: 6000/3000 MS (Java/Others)    Memory Limit: 131072/65536 K (Java/Others)
Total Submission(s): 1334    Accepted Submission(s): 410

Problem Description

Bobo has a tree,whose vertices are conveniently labeled by 1,2,...,n.Each node has a weight wi. All the weights are distrinct.
A set with m nodes v1,v2,...,vm is a Bobo Set if:
- The subgraph of his tree induced by this set is connected.
- After we sort these nodes in set by their weights in ascending order,we get u1,u2,...,um,(that is,wui<wui+1 for i from 1 to m-1).For any node x in the path from ui to ui+1(excluding ui and ui+1),should satisfy wx<wui.
Your task is to find the maximum size of Bobo Set in a given tree.

 

Input

The input consists of several tests. For each tests:
The first line contains a integer n (1≤n≤500000). Then following a line contains n integers w1,w2,...,wn (1≤wi≤109,all the wi is distrinct).Each of the following n-1 lines contain 2 integers ai and bi,denoting an edge between vertices ai and bi (1≤ai,bi≤n).
The sum of n is not bigger than 800000.

 

Output

For each test output one line contains a integer,denoting the maximum size of Bobo Set.

 

Sample Input

7

3 30 350 100 200 300 400

1 2

2 3

3 4

4 5

5 6

6 7

 

Sample Output

5

 

Author

ZSTU

 

Source

2015 Multi-University Training Contest 3

 

 解题：直接搜索。。。建立有向图时候，小权向大权的连边，然后看看每个每个点，最多能走多少个点。

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <cstring>
#pragma comment(linker, "/stack:1024000000,1024000000")
using namespace std;
const int maxn = 500010;
vector<int>g[maxn];
int w[maxn],ret[maxn];
void dfs(int u) {
    ret[u] = 1;
    for(int i = g[u].size()-1; i >= 0; --i) {
        if(!ret[g[u][i]]) dfs(g[u][i]);
        ret[u] += ret[g[u][i]];
    }
}
int main() {
    int n,u,v;
    while(~scanf("%d",&n)){
        for(int i = 1; i <= n; ++i){
            scanf("%d",w+i);
            g[i].clear();
        }
        for(int i = 1; i < n; ++i){
            scanf("%d%d",&u,&v);
            if(w[u] < w[v]) g[u].push_back(v);
            else g[v].push_back(u);
        }
        memset(ret,0,sizeof ret);
        int ans = 0;
        for(int i = 1; i <= n; ++i){
            if(!ret[i]) dfs(i);
            ans = max(ans,ret[i]);
        }
        printf("%d
",ans);
    }
    return 0;
}