CCF CSP 数据中心 c++ python csp201812_4 100分

CCF CSP 数据中心 c++ python csp201812_4 100分

样例输入
4
5
1
1 2 3
1 3 4
1 4 5
2 3 8
3 4 2
样例输出
4
样例说明
　　下图是样例说明。

问题分析
        这道题理解了题意后，其实就是求图的最小生成树，那个根没有一点用，根本不用考虑，只需要求出最小生成树的最大权值就ok了。传统的求最小生成树的算法有Prim算法和kruskal算法。但这篇博客我使用并查集的方法去解决。如果对并查集不了解的可以先去查查并查集。具体代码如下：
c++代码如下：

#include<cstdio>
#include<vector>
#include<algorithm>
using namespace std;
struct Edge{
	int from;
	int to;
	int distance;
}; 
int father[50005];
bool cmp(Edge e1,Edge e2){
		return e1.distance < e2.distance;
}
int result = 0;
int main(){
	void init(int number);
	void unio(int from,int to,int distance);
	int vertextNumber,edgeNumber,root;
	scanf("%d%d%d",&vertextNumber,&edgeNumber,&root);
	vector<Edge> vec;
	Edge temp;
	int from,to,distance;
	for(int i = 0;i < edgeNumber;i++){
		scanf("%d%d%d",&from,&to,&distance);
		temp.from = from;
		temp.to = to;
		temp.distance = distance;
		vec.push_back(temp);
	}
	sort(vec.begin(),vec.end(),cmp);
	init(vertextNumber);
	for(int i = 0;i < vec.size();i++){
		temp = vec[i];
		from = temp.from;
		to = temp.to;
		distance = temp.distance;
		unio(from,to,distance);
	}
	printf("%d\n",result);
	return 0;
}
void init(int number){
	for(int i = 0;i <= number;i++){
		father[i] = i;
	}
}
int findFather(int x){
	int a = x;
	while(x != father[x]){
		x = father[x];
	}
	while(a != father[a]){
		int z = father[a];
		father[a] = x;
		a = z;
	}
	return x;
}
void unio(int from,int to,int distance){
	int fx = findFather(from);
	int fy = findFather(to);
	if(fx != fy){
		father[fx] = fy;
		result = distance;
	}
}

java代码如下：

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

public class csp201812_4 {
	public static int edgeNumber;
	public static int[] father;
	public static int result;
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		edgeNumber = input.nextInt();
		int number = input.nextInt();
		int root = input.nextInt();
		List<Edge> list = new ArrayList<>();
		int from,to,distance;
		for(int i = 0;i < number;i++) {
			from = input.nextInt();
			to = input.nextInt();
			distance = input.nextInt();
			list.add(new Edge(from,to,distance));
		}
		init();
		Collections.sort(list);
		Edge temp;
		for(int i = 0;i < list.size();i++) {
			temp = list.get(i);
			Union(temp.from,temp.to,temp.distance);
		}
		System.out.println(result);
		input.close();
	}
	public static void init() {
		result = 0;
		father = new int[edgeNumber + 1];
		for(int i = 0;i < father.length;i++) {
			father[i] = i;
		}
	}
	public static int findFather(int x) {
		int a = x;
		while(x != father[x]) {
			x = father[x];
		}
		while(a != father[a]) {
			int z = a;
			a = father[a];
			father[z] = x; 
		}
		return x;
	}
	public static void Union(int x,int y,int dd) {
		int fx = findFather(x);
		int fy = findFather(y);
		if(fx != fy) {
			father[fx] = fy;
			result = dd;
		}
	}
}
class Edge implements Comparable<Edge>{
	public int from;
	public int to;
	public int distance;
	public Edge(int from, int to, int distance) {
		super();
		this.from = from;
		this.to = to;
		this.distance = distance;
	}
	@Override
	public int compareTo(Edge o) {
		return this.distance > o.distance ? 1 : this.distance < o.distance ? -1 : 0;
	}
}

由于java代码运行时间比较长，故提交后运行超时，只能得80分。
python3代码如下：

from operator import attrgetter
class Edge(object):
    def __init__(self,From,to,distance):
        self.From = From
        self.to = to
        self.distance = distance
father = []
result = 0
def init(number):
    for i in range(number):
        father.append(i)
def findFather(x):
    a = x
    while x != father[x]:
        x = father[x]
    while a != father[a]:
        z = father[a]
        father[a] = x
        a = z
    return x
def union(From, to, distance):
    global result
    fx = findFather(From)
    fy = findFather(to)
    if fx != fy:
        father[fx] = fy
        result = distance
if __name__ == '__main__':
    vertexNumber = (int)(input())
    edgeNumber = (int)(input())
    root = (int)(input())
    lists = []
    for i in range(edgeNumber):
        temp = input().split(" ")
        From = (int)(temp[0])
        to = (int)(temp[1])
        distance = (int)(temp[2])
        edge = Edge(From, to, distance)
        lists.append(edge)
    init(vertexNumber + 1)
    lists = sorted(lists, key=attrgetter('distance'))
    for i in range(edgeNumber):
        temp = lists[i]
        From = temp.From
        to = temp.to
        distance = temp.distance
        union(From, to, distance)
    print(result)

ok!大功告成了，如果你有更好的方法，可以在评论区交流哦！