g1201_1300.s1219_path_with_maximum_gold.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated
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package g1201_1300.s1219_path_with_maximum_gold;

// #Medium #Array #Matrix #Backtracking #2022_03_11_Time_48_ms_(57.00%)_Space_41.9_MB_(39.12%)

/**
 * 1219 - Path with Maximum Gold\.
 *
 * Medium
 *
 * In a gold mine `grid` of size `m x n`, each cell in this mine has an integer representing the amount of gold in that cell, `0` if it is empty.
 *
 * Return the maximum amount of gold you can collect under the conditions:
 *
 * *   Every time you are located in a cell you will collect all the gold in that cell.
 * *   From your position, you can walk one step to the left, right, up, or down.
 * *   You can't visit the same cell more than once.
 * *   Never visit a cell with `0` gold.
 * *   You can start and stop collecting gold from **any** position in the grid that has some gold.
 *
 * **Example 1:**
 *
 * **Input:** grid = \[\[0,6,0],[5,8,7],[0,9,0]]
 *
 * **Output:** 24
 *
 * **Explanation:** 
 *     
 *     [[0,6,0], 
 *      [5,8,7], 
 *      [0,9,0]] 
 *     Path to get the maximum gold, 9 -> 8 -> 7.
 *
 * **Example 2:**
 *
 * **Input:** grid = \[\[1,0,7],[2,0,6],[3,4,5],[0,3,0],[9,0,20]]
 *
 * **Output:** 28
 *
 * **Explanation:** 
 *
 *     [[1,0,7], 
 *      [2,0,6], 
 *      [3,4,5], 
 *      [0,3,0], 
 *      [9,0,20]] 
 *     Path to get the maximum gold, 1 -> 2 -> 3 -> 4 -> 5 -> 6 -> 7.
 *
 * **Constraints:**
 *
 * *   `m == grid.length`
 * *   `n == grid[i].length`
 * *   `1 <= m, n <= 15`
 * *   `0 <= grid[i][j] <= 100`
 * *   There are at most **25** cells containing gold.
**/
public class Solution {
    private int maxGold = 0;

    public int getMaximumGold(int[][] grid) {
        for (int i = 0; i < grid.length; i++) {
            for (int j = 0; j < grid[0].length; j++) {
                if (grid[i][j] != 0) {
                    int g = grid[i][j];
                    grid[i][j] = 0;
                    gold(grid, i, j, g);
                    grid[i][j] = g;
                }
            }
        }
        return maxGold;
    }

    private void gold(int[][] grid, int row, int col, int gold) {
        if (gold > maxGold) {
            maxGold = gold;
        }
        if (row > 0 && grid[row - 1][col] != 0) {
            int currGold = grid[row - 1][col];
            grid[row - 1][col] = 0;
            gold(grid, row - 1, col, gold + currGold);
            grid[row - 1][col] = currGold;
        }
        if (col > 0 && grid[row][col - 1] != 0) {
            int currGold = grid[row][col - 1];
            grid[row][col - 1] = 0;
            gold(grid, row, col - 1, gold + currGold);
            grid[row][col - 1] = currGold;
        }
        if (row < grid.length - 1 && grid[row + 1][col] != 0) {
            // flag=false;
            int currGold = grid[row + 1][col];
            grid[row + 1][col] = 0;
            gold(grid, row + 1, col, gold + currGold);
            grid[row + 1][col] = currGold;
        }
        if (col < grid[0].length - 1 && grid[row][col + 1] != 0) {
            int currGold = grid[row][col + 1];
            grid[row][col + 1] = 0;
            gold(grid, row, col + 1, gold + currGold);
            grid[row][col + 1] = currGold;
        }
    }
}