排序4个不带数组的数字 [英] Sort 4 numbers without array

问题描述

我有一个练习，需要将4个数字升序排列，然后不使用数组而降序.我只能使用循环和if语句.我已经用3个数字做到了，但是现在用4个数字我无法想到逻辑.

I have an exercise where I need to put 4 numbers in ascending order and then descending without using arrays. I can only use loops and if statements. I've done it with 3 numbers, but now with 4 numbers I am unable to think of the logic.

  float great1 = 0, great2 = 0, great3 = 0, great4 = 0;
  int a = 7, b = 5, c = 6, d = 0;

  // Descending
  if (a > b && b > c) {
    great1 = a;
    great2 = b;
    great3 = c;

  } else if (a > b && b < c) {
    great1 = a;
    great2 = c;
    great3 = b;

  } else if (b > a && a > c) {
    great1 = b;
    great2 = a;
    great3 = c;

  } else if (b > a && a < c) {
    great1 = b;
    great2 = c;
    great3 = a;

  } else if (c > a && a > b) {
    great1 = c;
    great2 = a;
    great3 = b;
  }

  else {
    great1 = c;
    great2 = b;
    great3 = a;
  }

推荐答案

一种进行固定大小的小型排序的好方法是使用分拣网络:

A nice way to do small, fixed-size sorts is using a sorting network:

int tmp;
if (a > b) { tmp = a; a = b; b = tmp; }
if (c > d) { tmp = c; c = d; d = tmp; }
if (a > c) { tmp = a; a = c; c = tmp; }
if (b > d) { tmp = b; b = d; d = tmp; }
if (b > c) { tmp = b; b = c; c = tmp; }

每行代码都对两个元素之间的比较和交换进行编码.

Each line codes a comparison and swap between two elements.

您可以使用此页面生成少量的最佳分类网络.输入.

You can use this page to generate optimal sorting networks for small numbers of inputs.

要以相反的顺序排序，只需将>符号翻转为<符号.

To sort in reverse order, just flip the > signs to < signs.

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