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package class17;
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import java.util.Comparator;
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import java.util.PriorityQueue;
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// 本题测试链接 : https://leetcode.com/problems/kth-smallest-element-in-a-sorted-matrix/
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public class Code02_KthSmallestElementInSortedMatrix {
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// 堆的方法
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public static int kthSmallest1(int[][] matrix, int k) {
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int N = matrix.length;
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int M = matrix[0].length;
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PriorityQueue<Node> heap = new PriorityQueue<>(new NodeComparator());
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boolean[][] set = new boolean[N][M];
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heap.add(new Node(matrix[0][0], 0, 0));
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set[0][0] = true;
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int count = 0;
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Node ans = null;
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while (!heap.isEmpty()) {
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ans = heap.poll();
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if (++count == k) {
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break;
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}
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int row = ans.row;
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int col = ans.col;
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if (row + 1 < N && !set[row + 1][col]) {
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heap.add(new Node(matrix[row + 1][col], row + 1, col));
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set[row + 1][col] = true;
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}
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if (col + 1 < M && !set[row][col + 1]) {
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heap.add(new Node(matrix[row][col + 1], row, col + 1));
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set[row][col + 1] = true;
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}
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}
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return ans.value;
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}
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public static class Node {
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public int value;
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public int row;
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public int col;
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public Node(int v, int r, int c) {
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value = v;
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row = r;
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col = c;
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}
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}
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public static class NodeComparator implements Comparator<Node> {
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@Override
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public int compare(Node o1, Node o2) {
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return o1.value - o2.value;
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}
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}
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// 二分的方法
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public static int kthSmallest2(int[][] matrix, int k) {
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int N = matrix.length;
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int M = matrix[0].length;
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int left = matrix[0][0];
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int right = matrix[N - 1][M - 1];
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int ans = 0;
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while (left <= right) {
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int mid = left + ((right - left) >> 1);
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// <=mid 有几个 <= mid 在矩阵中真实出现的数，谁最接近mid
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Info info = noMoreNum(matrix, mid);
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if (info.num < k) {
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left = mid + 1;
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} else {
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ans = info.near;
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right = mid - 1;
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}
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}
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return ans;
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}
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public static class Info {
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public int near;
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public int num;
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public Info(int n1, int n2) {
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near = n1;
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num = n2;
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}
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}
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public static Info noMoreNum(int[][] matrix, int value) {
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int near = Integer.MIN_VALUE;
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int num = 0;
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int N = matrix.length;
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int M = matrix[0].length;
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int row = 0;
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int col = M - 1;
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while (row < N && col >= 0) {
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if (matrix[row][col] <= value) {
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near = Math.max(near, matrix[row][col]);
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num += col + 1;
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row++;
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} else {
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col--;
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}
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}
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return new Info(near, num);
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}
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}
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