CodeForces 246D. Colorful Graph【STL】

本文介绍了一种算法,用于解决在一个彩色无向图中找到拥有最多不同相邻颜色节点的问题。通过使用map和set数据结构,文章详细展示了如何遍历图中的每条边,并计算各颜色的相邻不同颜色数量。

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D. Colorful Graph
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

You've got an undirected graph, consisting of n vertices and m edges. We will consider the graph's vertices numbered with integers from 1 to n. Each vertex of the graph has a color. The color of the i-th vertex is an integerci.

Let's consider all vertices of the graph, that are painted some color k. Let's denote a set of such as V(k). Let's denote the value of the neighbouring color diversity for color k as the cardinality of the set Q(k) = {cu :  cu ≠ kand there is vertex v belonging to set V(k) such that nodes v and u are connected by an edge of the graph}.

Your task is to find such color k, which makes the cardinality of set Q(k) maximum. In other words, you want to find the color that has the most diverse neighbours. Please note, that you want to find such color k, that the graph has at least one vertex with such color.

Input

The first line contains two space-separated integers n, m (1 ≤ n, m ≤ 105) — the number of vertices end edges of the graph, correspondingly. The second line contains a sequence of integers c1, c2, ..., cn (1 ≤ ci ≤ 105) — the colors of the graph vertices. The numbers on the line are separated by spaces.

Next m lines contain the description of the edges: the i-th line contains two space-separated integers ai, bi(1 ≤ ai, bi ≤ nai ≠ bi) — the numbers of the vertices, connected by the i-th edge.

It is guaranteed that the given graph has no self-loops or multiple edges.

Output

Print the number of the color which has the set of neighbours with the maximum cardinality. It there are multiple optimal colors, print the color with the minimum number. Please note, that you want to find such color, that the graph has at least one vertex with such color.

Examples
input
6 6
1 1 2 3 5 8
1 2
3 2
1 4
4 3
4 5
4 6
output
3
input
5 6
4 2 5 2 4
1 2
2 3
3 1
5 3
5 4
3 4
output
2

题意:

题目说,每个顶点对应一种颜色,可以相同。给出连接这些顶点的若干条边,定义Q(k)是所有颜色为k的所有顶点相连的不同的颜色的总数量(不包含k),求使得Q(k)最大时的k的值,如果有多个k 值满足,输出最小的k值.....


题解:

题目看了好久才看明白....英语水平确实很伤.....

需要用map和set ,因为数据给的比较小,直接暴力进行,否则则需要进行离散化对应(不会...)...


/*
http://blog.youkuaiyun.com/liuke19950717
*/
#include<cstdio>
#include<cstring>
#include<map>
#include<set>
using namespace std;
const int maxn=100005;
set<int> vis[maxn];
void init()
{
	for(int i=0;i<maxn;++i)
	{
		vis[i].clear();
	}
}
int main()
{
	int n,m;
	while(~scanf("%d%d",&n,&m))
	{
		init();
		map<int,int> map;
		for(int i=1;i<=n;++i)
		{
			int a;
			scanf("%d",&a);
			map[i]=a;
		}
		for(int i=0;i<m;++i)
		{
			int a,b;
			scanf("%d%d",&a,&b);
			if(map[a]!=map[b])//和自身相等的颜色不算
			{
				vis[map[a]].insert(map[b]);
				vis[map[b]].insert(map[a]);
			}
		}
		int ans=map[1];
		for(int i=1;i<=n;++i)
		{
			if(vis[ans].size()<vis[map[i]].size()||
			vis[ans].size()==vis[map[i]].size()&&ans>map[i])//判断条件
			{
				ans=map[i];
			}
		}
		printf("%d\n",ans);
	}
	return 0;
}




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