class Solution {
    public int numIslandsForReal(char[][] grid, Stack<Integer> stack, int row, int col, int numberOfRows, int numberOfCols, int count, int tempRow, int tempCol) {
        if ((grid[row][col] == '0') || (grid[row][col] == '9')){
            return count;
        }
        if (isValid(grid, row, col, numberOfCols, numberOfRows)){
            tempRow = stack.pop();
            tempCol = stack.pop();
            if (grid[tempRow][tempCol] == '1'){
                grid[tempRow][tempCol] = '9';
                stack.push(tempRow+1);
                stack.push(tempCol+1);
                count = numIslandsForReal(grid, stack, row+1, col+1, numberOfRows, numberOfCols, count, tempRow, tempCol);
            }
        }
        count++;
        return count;
    }

    public boolean isValid(char[][] grid, int row, int col, int numberOfCols, int numberOfRows){
        if ((row < numberOfRows) && (col < numberOfCols) && (row >= 0) && (col >= 0)){
            return true;
        }
        else{
            return false;
        }
    }

    public int numIslands(char[][] grid)
    {
        Stack<Integer> stack = new Stack<Integer>();
        int row = 0;
        int col = 0;
        int numberOfRows = grid.length;
        int numberOfCols = grid[0].length;
        int tempRow = 0;
        int tempCol = 0;
        int count = 0;
        stack.push(0); //row
        stack.push(0); //col
        return numIslandsForReal(grid, stack, row, col, numberOfRows, numberOfCols, count, tempRow, tempCol);
    }
}