[BOJ] 1504. 특정한 최단 경로 : https://www.acmicpc.net/problem/1504. 플로이드

특정한 최단 경로.cc

//
//  Created by fpdjsns
//  Copyright © 2019 fpdjsns. All rights reserved.
//

#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;

/*
 * 시간복잡도 : O(N^3)
 * 공간복잡도 : O(N^2)
 */
int main() {

	int N, E;
	cin >> N >> E;

	vector<vector<int>> dist(N, vector<int>(N, 1e6));

	int a, b, c;
	for (int i = 0; i < E; i++) {
		cin >> a >> b >> c;
		a--;
		b--;
		dist[a][b] = c;
		dist[b][a] = c;
	}
	for (int i = 0; i < N; i++) dist[i][i] = 0;

	for (int k = 0; k < N; k++) {
		for (int i = 0; i < N; i++) {
			for (int j = 0; j < N; j++) {
				dist[i][j] = min(dist[i][j], dist[i][k] + dist[k][j]);
			}
		}
	}

	cin >> a >> b;
	a--; b--;

	int ans = min(dist[0][a] + dist[a][b] + dist[b][N - 1], dist[0][b] + dist[b][a] + dist[a][N - 1]);
	if (ans > 1e6) ans = -1;
	printf("%d", ans);

	return 0;
}