LeetCode 1337. The K Weakest Rows in a Matrix

[Woodyiiiiiii]

1. 用优先队列排序
2. 用双指针查找边界

class Solution {
    public int[] kWeakestRows(int[][] mat, int k) {

        int m = mat.length, n = mat[0].length;

        PriorityQueue<int[]> pq = new PriorityQueue<>((o1, o2) -> o1[0] == o2[0] ? o1[1] - o2[1] : o1[0] - o2[0]);

        for (int i = 0; i < m; ++i) {
            int l = 0, r = n - 1;
            while (l <= r) {
                int mid = l + (r - l) / 2;
                if (mat[i][mid] == 1) {
                    l = mid + 1;
                } else {
                    r = mid - 1;
                }
            }
            pq.offer(new int[]{l, i});
        }

        int[] ans = new int[k];
        for (int i = 0; i < k; ++i) {
            if (!pq.isEmpty()) {
                int[] poll = pq.poll();
                ans[i] = poll[1];
            }
        }

        return ans;

    }
}