leetcode-200 岛屿数量

/**
 * @param {character[][]} grid
 * @return {number}
 */
var numIslands = function (grid) {
  if (!grid || grid.length === 0) return 0;
  const row = grid.length,
    col = grid[0].length;
  let islandCount = 0;
  function dfs(r, c) {
    if (r < 0 || c < 0 || r >= row || c >= col || grid[r][c] === "0") {
      return;
    }
    grid[r][c] = "0";
    dfs(r - 1, c);
    dfs(r + 1, c);
    dfs(r, c - 1);
    dfs(r, c + 1);
  }
  for (let r = 0; r < row; r++) {
    for (let c = 0; c < col; c++) {
      if (grid[r][c] === "1") {
        islandCount++;
        dfs(r, c);
      }
    }
  }
  return islandCount;
};