200. 岛屿数量

class Solution {
  void DFS(vector<vector<char>> &G, int X, int Y) {
    int Height = G.size(), Width = G.front().size();
    if (G[Y][X] == '0')
      return;

    // Boom!
    G[Y][X] = '0';
    if (X - 1 >= 0)
      DFS(G, X - 1, Y);
    if (X + 1 < Width)
      DFS(G, X + 1, Y);
    if (Y - 1 >= 0)
      DFS(G, X, Y - 1);
    if (Y + 1 < Height)
      DFS(G, X, Y + 1);
  }
public:
  int numIslands(vector<vector<char>>& grid) {
    int Result = 0;
    int Height = grid.size(), Width = grid.front().size();
    for (int y = 0; y < Height; ++y) {
      for (int x = 0; x < Width; ++x) {
        if (grid[y][x] == '1') {
          DFS(grid, x, y);
          ++Result;
        }
      }
    }
    return Result;
  }
};