695.cpp

// dfs.cpp
class Solution {
  int row, col;
  int dfs(vector<vector<int>> &grid, vector<vector<int>> &visited, int i,
          int j) {
    if (i < 0 || i >= row || j < 0 || j >= col || visited[i][j] ||
        grid[i][j] == 0)
      return 0;
    visited[i][j] = 1;
    return 1 + dfs(grid, visited, i + 1, j) + dfs(grid, visited, i, j + 1) +
           dfs(grid, visited, i - 1, j) + dfs(grid, visited, i, j - 1);
  }

public:
  int maxAreaOfIsland(vector<vector<int>> &grid) {
    row = grid.size();
    if (row == 0)
      return 0;
    col = grid[0].size();
    int maxArea = 0;
    vector<vector<int>> visited(row, vector<int>(col, 0));
    for (int i = 0; i < row; ++i)
      for (int j = 0; j < col; ++j)
        if (visited[i][j] == 0 && grid[i][j] == 1)
          maxArea = max(maxArea, dfs(grid, visited, i, j));
    return maxArea;
  }
};