Ref: https://pdai.tech/md/algorithm/alg-core-search.html

广度优先搜索（Depth-First Search，DFS）

2.经典案例

2.1 岛屿连通面积

Ref: https://leetcode-cn.com/problems/max-area-of-island/
image.png

  1. private int m, n;
  2. private int[][] direction = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
  4. public int maxAreaOfIsland(int[][] grid) {
  5.     if (grid == null || grid.length == 0) {
  6.         return 0;
  7.     }
  8.     m = grid.length;
  9.     n = grid[0].length;
  10.     int maxArea = 0;
  11.     for (int i = 0; i < m; i++) {
  12.         for (int j = 0; j < n; j++) {
  13.             maxArea = Math.max(maxArea, dfs(grid, i, j));
  14.         }
  15.     }
  16.     return maxArea;
  17. }
  19. private int dfs(int[][] grid, int r, int c) {
  20.     if (r < 0 || r >= m || c < 0 || c >= n || grid[r][c] == 0) {
  21.         return 0;
  22.     }
  23.     grid[r][c] = 0;
  24.     int area = 1;
  25.     for (int[] d : direction) {
  26.         area += dfs(grid, r + d[0], c + d[1]);
  27.     }
  28.     return area;
  29. }