2009合肥网赛H题解题报告

最新推荐文章于 2025-01-15 18:40:27 发布

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本文介绍了一种利用Dijkstra算法解决最短路径问题的方法，并通过一个具体的编程实例展示了如何求解两点间及其与其他各点间的最短路径。该实例采用Java实现，适用于竞赛或实际项目中寻找最优路径的问题。

这道题先直接求出每个点到其他点的最短距离，然后再枚举每一种组合。可以用dijkstra或者floyed都行！

http://acm.ustc.edu.cn/ustcoj/problem.php?id=1123

team579

Accepted

Java

1600ms

27672kb

2307

import java.util.Arrays; import java.util.Scanner; public class Main { private static int n; private static int[][] dist = new int[501][501]; public static void main(String[] args) { Scanner sc = new Scanner(System.in); int testNum = sc.nextInt(); for (int i = 0; i < testNum; i++) { n = sc.nextInt(); int e = sc.nextInt(); int[][] map = new int[e + 1][e + 1]; boolean[] visted = new boolean[n + 1]; for (int j = 1; j <= e; j++) { int a = sc.nextInt(); int b = sc.nextInt(); int t = sc.nextInt(); if (a == b) continue; else if (map[a][b] == 0) { map[a][b] = t; map[b][a] = t; } else if (map[a][b] != 0 && map[a][b] > t) { map[a][b] = t; map[b][a] = t; } } solve(map, visted); } } public static void solve(int[][] map, boolean[] visted) { int sum = Integer.MAX_VALUE; int ans1 = -1; int ans2 = -1; for (int i = 1; i <= n; i++) { dijkstra(map, visted, dist[i], i); } for (int i = 1; i < n; i++) { for (int j = i + 1; j <= n; j++) { int tempSum = 0; for (int k = 1; k <= n; k++) { if (dist[i][k] != Integer.MAX_VALUE && dist[j][k] != Integer.MAX_VALUE && k != i && k != j) { if (dist[i][k] > dist[j][k]) { tempSum += dist[j][k]; } else { tempSum += dist[i][k]; } } } if (sum > tempSum) { sum = tempSum; ans1 = i; ans2 = j; } } } System.out.println(ans1 + " " + ans2); } public static void dijkstra(int[][] map, boolean[] visted, int[] dist, int s) { Arrays.fill(visted, false); Arrays.fill(dist, Integer.MAX_VALUE); for (int i = 1; i <= n; i++) { if (map[s][i] != 0 && !visted[i]) dist[i] = map[s][i]; } visted[s] = true; int temp = 0; while (true) { int min = Integer.MAX_VALUE; temp = 0; for (int i = 1; i <= n; i++) { if (!visted[i] && min > dist[i]) { min = dist[i]; temp = i; } } if (temp == 0) break; visted[temp] = true; for (int i = 1; i <= n; i++) { if (!visted[i] && map[temp][i] != 0 && dist[i] > dist[temp] + map[temp][i]) { dist[i] = dist[temp] + map[temp][i]; } } } } }