TOJ：2870. The K-th City

最新推荐文章于 2017-11-17 23:51:04 发布

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本文介绍了一种用于解决最短路径问题的算法，包括如何构建道路映射、使用Floyd-Warshall算法求解最短路径以及如何对路径进行排序和筛选。通过实例演示了算法的具体应用。

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#include <iostream>
#include <cstring>
#include <algorithm>
#include <cstdio>
#define MAXN 205
#define MAX 500000
using namespace std;

int map[MAXN][MAXN];
int N, M, K, a, b, dis;

struct Road
{
	int city;
	int len;
} road[MAXN];

bool cmp(Road a, Road b)
{
	return a.len < b.len || (a.len == b.len && a.city < b.city);
}

void make()
{
	for (int i = 0; i < N; i++)
		for (int j = 0; j < N; j++)
		{
			map[i][j] = MAX;
			if (i == j)
				map[i][j] = 0;
		}
}

void solve()
{
	for (int k = 0; k < N; k++)
		for (int i = 0; i < N; i++)
			for (int j = 0; j < N; j++)
			{
				if (map[i][k] + map[k][j] < map[i][j])
				{
					map[i][j] = map[i][k] + map[k][j];
					map[j][i] = map[i][j];
				}
			}
			
	for (int i = 1; i < N; i++)
		road[i - 1].city = i, road[i - 1].len = map[0][i];
	sort(road, road + (N - 1), cmp);
	cout << road[K - 1].city << endl;
}

int main()
{
	while (cin >> N, N)
	{
		cin >> M;
		make();
		for (int i = 0; i < M; i++)
		{
			cin >> a >> b >> dis;
			map[a][b] = map[b][a] = dis;
		}
		cin >> K;
		solve();
	}
}