Function add

src/num-islands.js:6–17

(i, j, stack)

const numIslands = m => {
  const visited = [];
  const add = (i, j, stack) => {
    if (i < 0 || i >= m.length || j < 0 || j >= m[i].length || m[i][j] === '0') {
      return false;
    }
    if (visited[i] && visited[i][j]) {
      return false;
    }
    visited[i] = visited[i] || [];
    visited[i][j] = true;
    stack.push([i, j]);
    return true;
  };
  let total = 0;
  for (let i = 0; i < m.length; i += 1) {
    visited[i] = visited[i] || [];