像这种DFS相关的题型,重点还是要知道如何进行标记。我就是卡在这里顺不下去,难过死了……
public int closedIsland(int[][] grid) { int sum = 0; for(int i = 1;i<grid.length;i++){ for(int j = 1;j<grid[0].length;j++){ if(grid[i][j] == 0){ if(findIsland(grid,i,j)){ sum++; } } } } return sum; } private boolean findIsland(int[][] grid, int i, int j) { if(i<0||i>=grid.length||j<0||j>=grid[0].length){ return false; } if(grid[i][j] == 1){ return true; } grid[i][j] = 1; boolean up = findIsland(grid,i-1,j); boolean down = findIsland(grid,i+1,j); boolean left = findIsland(grid,i,j-1); boolean right = findIsland(grid,i,j+1); return up && down && left && right; }
用debug的方式很容易理解一道题解的思路。
——2020.6.21