g2501_2600.s2596_check_knight_tour_configuration.Solution Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of leetcode-in-java21 Show documentation

Java-based LeetCode algorithm problem solutions, regularly updated

There is a newer version: 1.38

package g2501_2600.s2596_check_knight_tour_configuration;

// #Medium #Array #Depth_First_Search #Breadth_First_Search #Matrix #Simulation
// #2023_08_29_Time_1_ms_(100.00%)_Space_43.4_MB_(42.62%)

/**
 * 2596 - Check Knight Tour Configuration\.
 *
 * Medium
 *
 * There is a knight on an `n x n` chessboard. In a valid configuration, the knight starts **at the top-left cell** of the board and visits every cell on the board **exactly once**.
 *
 * You are given an `n x n` integer matrix `grid` consisting of distinct integers from the range `[0, n * n - 1]` where `grid[row][col]` indicates that the cell `(row, col)` is the grid[row][col]^th cell that the knight visited. The moves are **0-indexed**.
 *
 * Return `true` _if_ `grid` _represents a valid configuration of the knight's movements or_ `false` _otherwise_.
 *
 * **Note** that a valid knight move consists of moving two squares vertically and one square horizontally, or two squares horizontally and one square vertically. The figure below illustrates all the possible eight moves of a knight from some cell.
 *
 * ![](https://assets.leetcode.com/uploads/2018/10/12/knight.png)
 *
 * **Example 1:**
 *
 * ![](https://assets.leetcode.com/uploads/2022/12/28/yetgriddrawio-5.png)
 *
 * **Input:** grid = \[\[0,11,16,5,20],[17,4,19,10,15],[12,1,8,21,6],[3,18,23,14,9],[24,13,2,7,22]]
 *
 * **Output:** true
 *
 * **Explanation:** The above diagram represents the grid. It can be shown that it is a valid configuration.
 *
 * **Example 2:**
 *
 * ![](https://assets.leetcode.com/uploads/2022/12/28/yetgriddrawio-6.png)
 *
 * **Input:** grid = \[\[0,3,6],[5,8,1],[2,7,4]]
 *
 * **Output:** false
 *
 * **Explanation:** The above diagram represents the grid. The 8^th move of the knight is not valid considering its position after the 7^th move.
 *
 * **Constraints:**
 *
 * *   `n == grid.length == grid[i].length`
 * *   `3 <= n <= 7`
 * *   `0 <= grid[row][col] < n * n`
 * *   All integers in `grid` are **unique**.
**/
public class Solution {
    public boolean checkValidGrid(int[][] grid) {
        if (grid[0][0] != 0) {
            return false;
        }
        int n = grid.length;
        int m = grid[0].length;
        int[] rmove = {2, 2, -2, -2, 1, 1, -1, -1};
        int[] cmove = {1, -1, 1, -1, 2, -2, 2, -2};
        int cnt = 0;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                int val = grid[i][j];
                boolean isPoss = false;
                for (int d = 0; d < 8; d++) {
                    int r = i + rmove[d];
                    int c = j + cmove[d];
                    if (r >= 0 && c >= 0 && r < n && c < m && grid[r][c] == val + 1) {
                        isPoss = true;
                    }
                }
                if (!isPoss) {
                    cnt++;
                }
                if (cnt > 1) {
                    return false;
                }
            }
        }
        return true;
    }
}