2022-02-11-12 1984. 学生分数的最小差值

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java版本

import  java.util.Arrays;
class Solution {
    public int minimumDifference(int[] nums, int k) {
    Arrays.sort(nums);
    // 选取k个
    k=k-1;
    int n=nums.length;
   
    if(k==0 || n==0){
        return 0;
    }
    int res=nums[k]-nums[0];
    for(int i=0;i<n-k;i++){
   
       res=Math.min(nums[i+k]-nums[i],res);
    }
    return res;

    }
}

1020. 飞地的数量
      DFS 注意，尽量返回结果的res尽量写在递归函数外面。
      java版本：

class Solution {
    public static int[][] dirs = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
    private int m, n;
    private boolean[][] visited;

    public int numEnclaves(int[][] grid) {
        m = grid.length;
        n = grid[0].length;
        visited = new boolean[m][n];
        for (int i = 0; i < m; i++) {
            dfs(grid, i, 0);
            dfs(grid, i, n - 1);
        }
        for (int j = 1; j < n - 1; j++) {
            dfs(grid, 0, j);
            dfs(grid, m - 1, j);
        }
        int enclaves = 0;
        for (int i = 1; i < m - 1; i++) {
            for (int j = 1; j < n - 1; j++) {
                if (grid[i][j] == 1 && !visited[i][j]) {
                    enclaves++;
                }
            }
        }
        return enclaves;
    }

    public void dfs(int[][] grid, int row, int col) {
        if (row < 0 || row >= m || col < 0 || col >= n || grid[row][col] == 0 || visited[row][col]) {
            return;
        }
        visited[row][col] = true;
        for (int[] dir : dirs) {
            dfs(grid, row + dir[0], col + dir[1]);
        }
    }
}