149 lines
5.0 KiB
Java
149 lines
5.0 KiB
Java
//有 n 个城市通过一些航班连接。给你一个数组 flights ，其中 flights[i] = [fromi, toi, pricei] ，表示该航班都从城
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//市 fromi 开始，以价格 pricei 抵达 toi。
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//
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// 现在给定所有的城市和航班，以及出发城市 src 和目的地 dst，你的任务是找到出一条最多经过 k 站中转的路线，使得从 src 到 dst 的 价格最便
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//宜 ，并返回该价格。 如果不存在这样的路线，则输出 -1。
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//
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//
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//
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// 示例 1：
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//
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//
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//输入:
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//n = 3, edges = [[0,1,100],[1,2,100],[0,2,500]]
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//src = 0, dst = 2, k = 1
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//输出: 200
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//解释:
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//城市航班图如下
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//
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//
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//从城市 0 到城市 2 在 1 站中转以内的最便宜价格是 200，如图中红色所示。
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//
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// 示例 2：
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//
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//
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//输入:
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//n = 3, edges = [[0,1,100],[1,2,100],[0,2,500]]
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//src = 0, dst = 2, k = 0
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//输出: 500
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//解释:
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//城市航班图如下
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//
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//
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//从城市 0 到城市 2 在 0 站中转以内的最便宜价格是 500，如图中蓝色所示。
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//
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//
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//
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// 提示：
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//
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//
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// 1 <= n <= 100
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// 0 <= flights.length <= (n * (n - 1) / 2)
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// flights[i].length == 3
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// 0 <= fromi, toi < n
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// fromi != toi
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// 1 <= pricei <= 10⁴
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// 航班没有重复，且不存在自环
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// 0 <= src, dst, k < n
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// src != dst
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//
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// Related Topics 深度优先搜索 广度优先搜索 图 动态规划 最短路 堆（优先队列） 👍 340 👎 0
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package leetcode.editor.cn;
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import com.code.leet.entiy.TwoArray;
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import java.util.*;
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//787:K 站中转内最便宜的航班
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class CheapestFlightsWithinKStops {
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public static void main(String[] args) {
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//测试代码
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Solution solution = new CheapestFlightsWithinKStops().new Solution();
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// TwoArray flights = new TwoArray("[[0,1,100],[1,2,100],[0,2,500]]", true);
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// System.out.println(solution.findCheapestPrice(3, flights.getArr(), 0, 2, 1));
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// TwoArray flights = new TwoArray("[[4,1,1],[1,2,3],[0,3,2],[0,4,10],[3,1,1],[1,4,3]]", true);
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// System.out.println(solution.findCheapestPrice(5, flights.getArr(), 2, 1, 1));
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TwoArray flights = new TwoArray("[[1,2,10],[2,0,7],[1,3,8],[4,0,10],[3,4,2],[4,2,10],[0,3,3],[3,1,6],[2,4,5]]", true);
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System.out.println(solution.findCheapestPrice(5, flights.getArr(), 0, 4, 1));
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}
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//力扣代码
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//leetcode submit region begin(Prohibit modification and deletion)
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class Solution {
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public int findCheapestPrice(int n, int[][] flights, int src, int dst, int k) {
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k++;
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Map<Integer, List<int[]>> prices = new HashMap<>();
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Queue<QueueEntity> queue = new LinkedList<>();
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int[] sums = new int[n];
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Arrays.fill(sums, Integer.MAX_VALUE);
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for (int[] flight : flights) {
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List<int[]> list = prices.getOrDefault(flight[0], new ArrayList<>());
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list.add(new int[]{flight[1], flight[2]});
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prices.put(flight[0], list);
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}
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queue.add(new QueueEntity(src, 0, new ArrayList<>(Collections.singletonList(src))));
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while (k > 0 && !queue.isEmpty()) {
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int size = queue.size();
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for (int i = 0; i < size; i++) {
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QueueEntity queueEntity = queue.poll();
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List<Integer> use = queueEntity.use;
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if (!prices.containsKey(queueEntity.flight)) {
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continue;
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}
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for (int[] arr : prices.get(queueEntity.flight)) {
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if (queueEntity.sum + arr[1] >= sums[arr[0]] || queueEntity.use.contains(arr[0])) {
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continue;
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}
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if (arr[0] != dst) {
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use.add(arr[0]);
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queue.add(new QueueEntity(arr[0], queueEntity.sum + arr[1], use));
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use.remove((Integer)arr[0]);
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}
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sums[arr[0]] = queueEntity.sum + arr[1];
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}
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}
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k--;
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}
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return sums[dst] == Integer.MAX_VALUE ? -1 : sums[dst];
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}
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class QueueEntity {
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int flight;
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int sum;
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List<Integer> use;
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public QueueEntity(int flight, int sum, List<Integer> use) {
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this.flight = flight;
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this.sum = sum;
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this.use = use;
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}
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public int getFlight() {
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return flight;
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}
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public void setFlight(int flight) {
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this.flight = flight;
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}
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public int getSum() {
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return sum;
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}
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public void setSum(int sum) {
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this.sum = sum;
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}
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public List<Integer> getUse() {
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return use;
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}
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public void setUse(List<Integer> use) {
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this.use = use;
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}
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}
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}
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//leetcode submit region end(Prohibit modification and deletion)
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} |