Java 二维数组按列排序及行列互换实现

import java.util.Arrays; import java.util.Comparator;

public class Main { public static void main(String[] args) { int[][] arr = new int[3][]; arr[0] = new int[]{10, 2, 3}; arr[1] = new int[]{4, 50, 6}; arr[2] = new int[]{7, 8, 90};

    f1(arr);
    System.out.println(Arrays.deepToString(arr));
}

// 使用 lambda，对二维数组按照第一列进行排序
public static void f1(int[][] arr) {
    Arrays.sort(arr, Comparator.comparingInt(a -> a[0]));
}

// 使用 lambda，对二维数组按照第二列进行排序
public static void f2(int[][] arr) {
    Arrays.sort(arr, Comparator.comparingInt(a -> a[1]));
}

// 行列互换，用于满足按行排序的需求
public static void f3(int[][] arr) {
    int[][] arr2 = new int[arr[0].length][arr.length];
    for (int i = 0; i < arr.length; i++) {
        for (int j = 0; j < arr[i].length; j++) {
            arr2[j][i] = arr[i][j];
        }
    }
    System.out.println(Arrays.deepToString(arr2));
    
    // 赋给原数组
    for (int i = 0; i < arr.length; i++) {
        for (int j = 0; j < arr[i].length; j++) {
            arr[i][j] = arr2[i][j];
        }
    }       
}

}