排序2维java数组 [英] sorting 2 dimensional java array

问题描述

我已经实现了冒泡排序来对二维java long [] []
进行排序但我的上帝很慢，我将需要禁食算法，因为
i将生成一个数组最大堆大小jvm将允许我，

I have implemented bubble sort to sort a two dimensional java long [][] but my god is it slow, I will be needing the fasted algorithm possible as i will be generating a array of the max heap size jvm will allow me,

所以我认为最好和最快的方法是使用inbuild java Arrays.sort

So i think the best and fastest way would be to use the inbuild java Arrays.sort

我不介意它是否只能排在第一列，因为我可以改变我的程序以适应，
我遇到过这个，但我不熟悉comaparator，

I dont mind if it can only sort on column one as i can change my program to suit, I came across this but am not to familar with comaparator,

这将允许我对一个整数的维数组排序，有没有人知道如何改变它以允许多头？，我做了思想家用它没有欢乐。

this will allow me to sort a dimensional array of integers, does anyone know how to change this to allow longs?, i did thinker around with it with no joy yet.

int d2 [][] = {{1,43},{26,98},{44,398},{11,34},{17,32}};

java.util.Arrays.sort(d2, new java.util.Comparator<int[]>() {
    public int compare(int[] a, int[] b) {
        return b[0] - a[0];
    }
});

我想排序说

long d2L [][] = {{1,43},{26,98},{44,398},{11,34},{17,32}};

铸造不是一个选项，因为数字是巨大的

casting is not an option as the numbers a massive

此外，如果有人认为这是一个更快的方法来排序我所有的耳朵：）

Also if anyone thinks theres a faster method to sort im all ears:)

推荐答案

这基于所有列排序在O（NlogN）中，即非常快：

This sorts based on all columns in O(NlogN), i.e. really fast:

import java.util.*;

class Compare2DArray implements Comparator {
  public int compare(Object a, Object b) {
    int aa[] = (int[]) a;
    int bb[] = (int[]) b;
    for (int i = 0; i < aa.length && i < bb.length; i++)
      if (aa[i] != bb[i])
        return aa[i] - bb[i];
    return aa.length - bb.length;
  }
}

class sort2d {
  public static void main(String args[]) {
    int d2 [][] = {{1,43},{26,98},{44,398},{11,34},{17,32}};
    Arrays.sort(d2, new Compare2DArray());
    for (int i = 0; i < d2.length; i++) {
      for (int j = 0; j < d2[i].length; j++)
        System.out.print(d2[i][j] + " ");
      System.out.println();
    }
  }
}

http://ideone.com/TjEOL

或者您可以使用泛型来避免cast：

Or you could use generics to avoid casting:

class Compare2DArray implements Comparator<int[]> {
  public int compare(int a[], int b[]) {
    for (int i = 0; i < a.length && i < b.length; i++)
      if (a[i] != b[i])
        return a[i] - b[i];
    return a.length - b.length;
  }
}

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