class Solution {
    private final int MAX_TASKS = 26;

    public int leastInterval(char[] tasks, int n) {
        int[] minStart = new int[MAX_TASKS];
        int[] counts = new int[MAX_TASKS];

        for (int i = 0; i < tasks.length; i++) {
            int task = tasks[i] - 'A';
            counts[task] = counts[task] + 1;
        }

        return go(0, minStart, counts, n, Integer.MAX_VALUE);
    }

    private int go(int position, int[] minStart, int[] counts, int idle, int minSoFar) {
        boolean noMoreTasks = true;

        for (int i = 0; i < MAX_TASKS; i++) {
            if (counts[i] > 0) {
                noMoreTasks = false;

                int next = Math.max(minStart[i], position);
                if (next >= minSoFar) {
                    continue;
                }

                counts[i] = counts[i] - 1;
                minStart[i] = next + idle + 1;

                int newMin = go(next, minStart, counts, idle, minSoFar);

                counts[i] = counts[i] + 1;
                minStart[i] = next;

                if (newMin < minSoFar) {
                    minSoFar = newMin;
                }
            }
        }

        if (noMoreTasks) {
            minSoFar = position + 1;
        }

        return minSoFar;
    }
}