solve 621.task-scheduler

Author: andavid

vscode/621.task-scheduler.java

@@ -0,0 +1,67 @@
+/*
+ * @lc app=leetcode id=621 lang=java
+ *
+ * [621] Task Scheduler
+ *
+ * https://leetcode.com/problems/task-scheduler/description/
+ *
+ * algorithms
+ * Medium (46.16%)
+ * Likes:    1885
+ * Dislikes: 332
+ * Total Accepted:    100.8K
+ * Total Submissions: 218K
+ * Testcase Example:  '["A","A","A","B","B","B"]\n2'
+ *
+ * Given a char array representing tasks CPU need to do. It contains capital
+ * letters A to Z where different letters represent different tasks. Tasks
+ * could be done without original order. Each task could be done in one
+ * interval. For each interval, CPU could finish one task or just be idle.
+ *
+ * However, there is a non-negative cooling interval n that means between two
+ * same tasks, there must be at least n intervals that CPU are doing different
+ * tasks or just be idle.
+ *
+ * You need to return the least number of intervals the CPU will take to finish
+ * all the given tasks.
+ *
+ *
+ *
+ * Example:
+ *
+ *
+ * Input: tasks = ["A","A","A","B","B","B"], n = 2
+ * Output: 8
+ * Explanation: A -> B -> idle -> A -> B -> idle -> A -> B.
+ *
+ *
+ *
+ *
+ * Note:
+ *
+ *
+ * The number of tasks is in the range [1, 10000].
+ * The integer n is in the range [0, 100].
+ *
+ *
+ */
+class Solution {
+  public int leastInterval(char[] tasks, int n) {
+    int[] map = new int[26];
+    for (char task : tasks) {
+      map[task - 'A']++;
+    }
+
+    Arrays.sort(map);
+
+    int max = map[25] - 1;
+    int idle = max * n;
+
+    for (int i = 24; i >= 0 && map[i] > 0; i--) {
+      idle -= (map[i] > max) ? max : map[i];
+    }
+
+    return (idle > 0) ? (tasks.length + idle) : tasks.length;
+  }
+}
+