DFS经典题，两种方法，递归或者用栈

1.递归

public class Solution{public int MaxAreaOfIsland(int[][] grid) {int rows = grid.Length;int cols = grid[0].Length;int res = 0;for(int i = 0; i < rows; i++){for(int j = 0; j < cols; j++){res = Max(res, DFS(grid, i, j, rows, cols));}}return res;}private int DFS(int[][] grid, int row, int col, int maxRow, int maxCol){if(row < 0 || row >= maxRow ||  col < 0 || col >= maxCol || grid[row][col] == 0 )return 0;else{grid[row][col] = 0;return 1 + DFS(grid, row - 1, col, maxRow, maxCol) + DFS(grid, row + 1, col, maxRow, maxCol) + DFS(grid, row, col - 1, maxRow, maxCol) + DFS(grid, row, col + 1, maxRow, maxCol);}}private int Max(int a, int b){return a > b? a : b;}}

2.栈

public class Solution{public int MaxAreaOfIsland(int[][] grid) {int rows = grid.Length;int cols = grid[0].Length;int res = 0;List<int[]> islandsStack = new List<int[]>();for(int i = 0; i < rows; i++){for(int j = 0; j < cols; j++){if(grid[i][j] != 0){islandsStack.Add(new int[2]{i,j});int tempRes = 0;while(islandsStack.Count != 0){tempRes += 1;int[] point = islandsStack[islandsStack.Count - 1];islandsStack.RemoveAt(islandsStack.Count - 1);grid[point[0]][point[1]] = 0;if(point[0] + 1 < rows && grid[point[0] + 1][point[1]] != 0){grid[point[0] + 1][point[1]] = 0;islandsStack.Add(new int[2]{point[0] + 1, point[1]});}if(point[0]- 1 >= 0 && grid[point[0] - 1][point[1]] != 0){grid[point[0] - 1][point[1]] = 0;islandsStack.Add(new int[2]{point[0] - 1, point[1]});}if(point[1] + 1 < cols && grid[point[0]][point[1] + 1] != 0){grid[point[0]][point[1] + 1] = 0;islandsStack.Add(new int[2]{point[0], point[1]+ 1});}if(point[1] - 1 >= 0 && grid[point[0]][point[1] - 1] != 0){grid[point[0]][point[1] - 1] = 0;islandsStack.Add(new int[2]{point[0], point[1] - 1});    }  }res = Max(res, tempRes);}}}return res;}private int Max(int a, int b){return a > b? a : b;}}