欢迎访问我的CCF认证解题目录
题目描述
思路过程
最开始我以为是求最小生成树的最大边。。。结果错了,重新看了一下题,发现A市决定在1号到n号枢纽间修建一条地铁
这句话,只要1和n联通了就好,最小生成树最大边的变形题,所以只要在最小生成树的模板上稍加修改即可,当1和n联通时,就结束循环,输出
代码
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Comparator;
import java.util.PriorityQueue;
public class Main {
public static int[] father = new int[100005];
public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String[] line = br.readLine().split(" ");
int n = Integer.parseInt(line[0]), m = Integer.parseInt(line[1]);
long max = Long.MIN_VALUE;
PriorityQueue<Edge> edges = new PriorityQueue<Edge>(new Comparator<Edge>() {
@Override
public int compare(Edge o1, Edge o2) {
return o1.cost - o2.cost; //按时间升序
}
});
//初始化
for ( int i = 1; i < n+1; i++ ) father[i] = i;
for ( int i = 0; i < m; i++ ) {
line = br.readLine().split(" ");
edges.offer(new Edge(Integer.parseInt(line[0]), Integer.parseInt(line[1]), Integer.parseInt(line[2])));
}
while ( findFather(1) != findFather(n) ) {//判断1和n是否已经联通
Edge temp = edges.poll();
int father1 = findFather(temp.v1), father2 = findFather(temp.v2);
if ( father1 != father2 ) {//如果父母不同,说明没有边连接
father[father1] = father2;
if ( temp.cost > max ) max = temp.cost;
}
}
System.out.println(max);
}
public static int findFather( int index ) { //路径压缩
if ( father[index] == index ) return index;
int temp = findFather(father[index]);
father[index] = temp;
return temp;
}
}
class Edge {
int v1,v2,cost;
public Edge(int v1, int v2, int cost) {
this.v1 = v1;
this.v2 = v2;
this.cost = cost;
}
}