Map of Highest Peak LeetCode solution in Java

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class Solution {
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  static int[][] DIRECTION = new int[][] {{0, -1}, {0, 1}, {-1, 0}, {1, 0}};
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  int rows;
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  int cols;
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  int[][] isWater;
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  public int[][] highestPeak(int[][] isWater) {
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    this.isWater = isWater;
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    rows = isWater.length;
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    cols = isWater[0].length;
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    int[][] heightCells = new int[rows][cols];
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    // store the coordinate of water cell
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    Queue<int[]> queue = new LinkedList();
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    for (int r = 0; r < rows; r++) {
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      for (int c = 0; c < cols; c++) {
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        if (isWater[r][c] == 1) {
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          // mark as water
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          heightCells[r][c] = 0;
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          // add water coordinate
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          queue.add(new int[] {r, c});
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        } else {
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          // mark default value for land
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          heightCells[r][c] = -1;
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        }
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      }
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    }
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    /*
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    * Approach
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    * 1. start from every water source,
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         update their neighbor height
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    * 2. add each neighbours which was not processed earlier
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      3. do it every cell is processed
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    */
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    bfs(queue, heightCells);
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    return heightCells;
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  }
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  private void bfs(Queue<int[]> queue, int[][] heightCells) {
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    while (!queue.isEmpty()) {
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      int[] cell = queue.remove();
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      // increment height of neighbor cell in all 4 direction
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      // e.g, left, right, up, down
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      for (int[] dir : DIRECTION) {
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        int newRow = cell[0] + dir[0];
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        int newCol = cell[1] + dir[1];
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        // check new coordinate of cell inside the grid or not
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        if (!isInsideGrid(newRow, newCol)) continue;
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        // check already handled
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        if (heightCells[newRow][newCol] != -1) continue;
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        // increament,
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        heightCells[newRow][newCol] = heightCells[cell[0]][cell[1]] + 1;
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        // to handle the neighbour of this new cell
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        queue.add(new int[] {newRow, newCol});
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      }
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    }
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  }
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  private boolean isInsideGrid(int row, int col) {
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    return row >= 0 && row < rows && col >= 0 && col < cols;
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  }
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}