Javascript Code Challange: RangeError: Maximum call stack size exceeded

Question

So basically I am trying to solve the 200. Number of Islands Leetcode challenge but I keep getting the above error. I know what the error implies but I can't spot the situation in my code. I have both a test file and the actual code file. There is an inner loop and recursion and the error keeps happening at the recursion function

index.js

function numIslands(grid) {
    let count = 0;
    //we would iterate over every cell in the matrix
    //we start by iterating over the row
    for (let row = 0; row < grid.length; row++) {
        //then iterate over column.
        //We use grid[0].length becuase all col at the same so we just take the first length
        for (let col = 0; col < grid[0].length; col++) {
            //if the current cell is 1
            if (grid[row][col] === '1') {
                //sink the island if a o

                count++;
                //this function is to sink the island
                //i.e turn to
                dfs(grid, row, col);
            }
        }
    }

    function dfs(grid, row, col) {
        //if row is less than  0 or out of bounds
        //if col is less than  0 or out of bounds vertically
        // or current cell is water, then end the function call,
        if (row < 0 || row >= grid.length || col < 0 || col >= grid[0].length || grid[row][col] === '0') {
            return;
        }
        //|| row >= grid.length || col < 0 || col >= grid[0].length || grid[row][col] === '0'
        // set the current cell to 0, i.e sink it
        grid[row][col] === '0';
        //check the cells to the left right top and bottom of current cell
        dfs(grid, row - 1, col); //left
        dfs(grid, row + 1, col); //right
        dfs(grid, row, col - 1); ///bottom
        dfs(grid, row, col + 1); ///top
    }

    return count;
}

test file

test("returns 0 islands correctly.", () => {
  expect(
    numIslands([
      ["0", "0", "0", "0", "0"],
      ["0", "0", "0", "0", "0"],
      ["0", "0", "0", "0", "0"]
    ])
  ).toEqual(0);
});

test("returns 1 island correctly.", () => {
  expect(
    numIslands([
      ["1", "1", "1", "1", "0"],
      ["1", "1", "0", "1", "0"],
      ["1", "1", "0", "0", "0"],
      ["0", "0", "0", "0", "0"],
      ["0", "0", "0", "0", "0"]
    ])
  ).toEqual(1);
});

test("returns 3 islands correctly.", () => {
  expect(
    numIslands([
      ["1", "1", "0", "0", "0"],
      ["1", "1", "0", "0", "0"],
      ["0", "0", "1", "0", "0"],
      ["0", "0", "0", "1", "1"]
    ])
  ).toEqual(3);
});

The error means that your recursion is never breaking due to the base case never being fulfilled. — Bob th
– Bob th, Commented Aug 11, 2022 at 17:40

Pantalaimon · Accepted Answer · 2022-08-11 17:44:55Z

4

The line

grid[row][col] === '0';

in the dfs function doesn't make sense. It's a comparison operator, and not an assignment operator.

It appears to be working with this line corrected.

grid[row][col] = '0';

answered Aug 11, 2022 at 17:44

Pantalaimon

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1 Comment

Udendu Abasili Over a year ago

wow, thanks. a ridiculous mistake on my part

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