2024/10/01 今日与昨日每日一题

src/main/java/com/cool/one_question_per_day/LeetCode20241001.java

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+package com.cool.one_question_per_day;
+
+/**
+ * Created with IntelliJ IDEA.
+ *
+ * @Author: Cool
+ * @Date: 2024/10/01/13:30
+ * DayNumber 1
+ * Hard 2
+ * Level 7
+ * Score 1786
+ * @Description 983. 最低票价
+ */
+public class LeetCode20241001 {
+    public int mincostTickets(int[] days, int[] costs) {
+        int lastDay = days[days.length - 1];
+        boolean[] isTravel = new boolean[lastDay + 1];
+        for (int d : days) {
+            isTravel[d] = true;
+        }
+        int[] memo = new int[lastDay + 1];
+        return dfs(lastDay, isTravel, costs, memo);
+    }
+
+    private int dfs(int i, boolean[] isTravel, int[] costs, int[] memo) {
+        if (i <= 0) {
+            return 0;
+        }
+        if (memo[i] > 0) { // 之前计算过
+            return memo[i];
+        }
+        if (!isTravel[i]) {
+            return memo[i] = dfs(i - 1, isTravel, costs, memo);
+        }
+        return memo[i] = Math.min(dfs(i - 1, isTravel, costs, memo) + costs[0],
+                Math.min(dfs(i - 7, isTravel, costs, memo) + costs[1],
+                        dfs(i - 30, isTravel, costs, memo) + costs[2]));
+    }
+}

src/main/java/com/cool/one_question_per_day/SeatManager.java

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+package com.cool.one_question_per_day;
+
+import java.util.Arrays;
+import java.util.PriorityQueue;
+
+/**
+ * Created with IntelliJ IDEA.
+ *
+ * @Author: Cool
+ * @Date: 2024/09/30/20:24
+ * DayNumber 3
+ * Level 3
+ * Score 1429
+ * Hard 2
+ * @link https://leetcode.cn/problems/seat-reservation-manager/description/?envType=daily-question&envId=2024-09-30
+ * @Description 1845. 座位预约管理系统
+ */
+public class SeatManager {
+    private final PriorityQueue<Integer> available = new PriorityQueue<>();
+    private int seats;
+
+    public SeatManager(int n) {
+    }
+
+    public int reserve() {
+        if (!available.isEmpty()) { // 有空出来的椅子
+            return available.poll(); // 坐编号最小的
+        }
+        return ++seats; // 添加一把新的椅子
+    }
+
+    public void unreserve(int seatNumber) {
+        available.add(seatNumber); // 有人离开了椅子
+    }
+
+
+//    boolean[] manager;
+//    int minIndex = 0;
+//
+//    public SeatManager(int n) {
+//        manager = new boolean[n];
+//        Arrays.fill(manager, true);
+//    }
+//
+//    public int reserve() {
+//        if (minIndex < manager.length) {
+//            while (!manager[minIndex]) {
+//                Q
+//                minIndex++;
+//            }
+//            manager[minIndex++] = false;
+//        }
+//        return minIndex;
+//    }
+//
+//    public void unreserve(int seatNumber) {
+//        manager[seatNumber - 1] = true;
+//        minIndex = Math.min(minIndex, seatNumber - 1);
+//    }
+
+}