java实现排列组合(通俗易懂)
Posted zzlback
tags:
篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了java实现排列组合(通俗易懂)相关的知识，希望对你有一定的参考价值。
个人感觉这篇文章(原文地址见文章尾)写的排列组合问题,非常的好,而且是一步一步引出排列组合问题,我也是看了这篇文章,一步一步按照这个思路来,最后会了自己的一套排列组合
也因此在算法竞赛中,两次用到了,成功解决了问题.
第一个问题:
首先,先让我们来看第一个问题, 有1,2,3,4这4个数字.可以重复的在里面选4次,问能得到多少种结果.easy
1 1 1 1
1 1 1 2
1 1 1 3
1 1 1 4
1 1 2 1
1 1 2 2
.......
4 4 4 3
4 4 4 4
代码实现其实也很简单,大家可以看下代码,理解一下,再自己敲一下,应该可以很快敲出来
import java.util.Stack;
public class Main {
public static Stack<Integer> stack = new Stack<Integer>();
public static void main(String[] args) {
int shu[] = {1,2,3,4};
f(shu,4,0);
}
/**
*
* @param shu 待选择的数组
* @param targ 要选择多少个次
* @param cur 当前选择的是第几次
*/
private static void f(int[] shu, int targ, int cur) {
// TODO Auto-generated method stub
if(cur == targ) {
System.out.println(stack);
return;
}
for(int i=0;i<shu.length;i++) {
stack.add(shu[i]);
f(shu, targ, cur+1);
stack.pop();
}
}
}
输出:
[1, 1, 1, 1] [1, 1, 1, 2] [1, 1, 1, 3] [1, 1, 1, 4] [1, 1, 2, 1] [1, 1, 2, 2] [1, 1, 2, 3] [1, 1, 2, 4] [1, 1, 3, 1] [1, 1, 3, 2] [1, 1, 3, 3] [1, 1, 3, 4] [1, 1, 4, 1] [1, 1, 4, 2] [1, 1, 4, 3] [1, 1, 4, 4] [1, 2, 1, 1] [1, 2, 1, 2] [1, 2, 1, 3] [1, 2, 1, 4] [1, 2, 2, 1] [1, 2, 2, 2] [1, 2, 2, 3] [1, 2, 2, 4] [1, 2, 3, 1] [1, 2, 3, 2] [1, 2, 3, 3] [1, 2, 3, 4] [1, 2, 4, 1] [1, 2, 4, 2] [1, 2, 4, 3] [1, 2, 4, 4] [1, 3, 1, 1] [1, 3, 1, 2] [1, 3, 1, 3] [1, 3, 1, 4] [1, 3, 2, 1] [1, 3, 2, 2] [1, 3, 2, 3] [1, 3, 2, 4] [1, 3, 3, 1] [1, 3, 3, 2] [1, 3, 3, 3] [1, 3, 3, 4] [1, 3, 4, 1] [1, 3, 4, 2] [1, 3, 4, 3] [1, 3, 4, 4] [1, 4, 1, 1] [1, 4, 1, 2] [1, 4, 1, 3] [1, 4, 1, 4] [1, 4, 2, 1] [1, 4, 2, 2] [1, 4, 2, 3] [1, 4, 2, 4] [1, 4, 3, 1] [1, 4, 3, 2] [1, 4, 3, 3] [1, 4, 3, 4] [1, 4, 4, 1] [1, 4, 4, 2] [1, 4, 4, 3] [1, 4, 4, 4] [2, 1, 1, 1] [2, 1, 1, 2] [2, 1, 1, 3] [2, 1, 1, 4] [2, 1, 2, 1] [2, 1, 2, 2] [2, 1, 2, 3] [2, 1, 2, 4] [2, 1, 3, 1] [2, 1, 3, 2] [2, 1, 3, 3] [2, 1, 3, 4] [2, 1, 4, 1] [2, 1, 4, 2] [2, 1, 4, 3] [2, 1, 4, 4] [2, 2, 1, 1] [2, 2, 1, 2] [2, 2, 1, 3] [2, 2, 1, 4] [2, 2, 2, 1] [2, 2, 2, 2] [2, 2, 2, 3] [2, 2, 2, 4] [2, 2, 3, 1] [2, 2, 3, 2] [2, 2, 3, 3] [2, 2, 3, 4] [2, 2, 4, 1] [2, 2, 4, 2] [2, 2, 4, 3] [2, 2, 4, 4] [2, 3, 1, 1] [2, 3, 1, 2] [2, 3, 1, 3] [2, 3, 1, 4] [2, 3, 2, 1] [2, 3, 2, 2] [2, 3, 2, 3] [2, 3, 2, 4] [2, 3, 3, 1] [2, 3, 3, 2] [2, 3, 3, 3] [2, 3, 3, 4] [2, 3, 4, 1] [2, 3, 4, 2] [2, 3, 4, 3] [2, 3, 4, 4] [2, 4, 1, 1] [2, 4, 1, 2] [2, 4, 1, 3] [2, 4, 1, 4] [2, 4, 2, 1] [2, 4, 2, 2] [2, 4, 2, 3] [2, 4, 2, 4] [2, 4, 3, 1] [2, 4, 3, 2] [2, 4, 3, 3] [2, 4, 3, 4] [2, 4, 4, 1] [2, 4, 4, 2] [2, 4, 4, 3] [2, 4, 4, 4] [3, 1, 1, 1] [3, 1, 1, 2] [3, 1, 1, 3] [3, 1, 1, 4] [3, 1, 2, 1] [3, 1, 2, 2] [3, 1, 2, 3] [3, 1, 2, 4] [3, 1, 3, 1] [3, 1, 3, 2] [3, 1, 3, 3] [3, 1, 3, 4] [3, 1, 4, 1] [3, 1, 4, 2] [3, 1, 4, 3] [3, 1, 4, 4] [3, 2, 1, 1] [3, 2, 1, 2] [3, 2, 1, 3] [3, 2, 1, 4] [3, 2, 2, 1] [3, 2, 2, 2] [3, 2, 2, 3] [3, 2, 2, 4] [3, 2, 3, 1] [3, 2, 3, 2] [3, 2, 3, 3] [3, 2, 3, 4] [3, 2, 4, 1] [3, 2, 4, 2] [3, 2, 4, 3] [3, 2, 4, 4] [3, 3, 1, 1] [3, 3, 1, 2] [3, 3, 1, 3] [3, 3, 1, 4] [3, 3, 2, 1] [3, 3, 2, 2] [3, 3, 2, 3] [3, 3, 2, 4] [3, 3, 3, 1] [3, 3, 3, 2] [3, 3, 3, 3] [3, 3, 3, 4] [3, 3, 4, 1] [3, 3, 4, 2] [3, 3, 4, 3] [3, 3, 4, 4] [3, 4, 1, 1] [3, 4, 1, 2] [3, 4, 1, 3] [3, 4, 1, 4] [3, 4, 2, 1] [3, 4, 2, 2] [3, 4, 2, 3] [3, 4, 2, 4] [3, 4, 3, 1] [3, 4, 3, 2] [3, 4, 3, 3] [3, 4, 3, 4] [3, 4, 4, 1] [3, 4, 4, 2] [3, 4, 4, 3] [3, 4, 4, 4] [4, 1, 1, 1] [4, 1, 1, 2] [4, 1, 1, 3] [4, 1, 1, 4] [4, 1, 2, 1] [4, 1, 2, 2] [4, 1, 2, 3] [4, 1, 2, 4] [4, 1, 3, 1] [4, 1, 3, 2] [4, 1, 3, 3] [4, 1, 3, 4] [4, 1, 4, 1] [4, 1, 4, 2] [4, 1, 4, 3] [4, 1, 4, 4] [4, 2, 1, 1] [4, 2, 1, 2] [4, 2, 1, 3] [4, 2, 1, 4] [4, 2, 2, 1] [4, 2, 2, 2] [4, 2, 2, 3] [4, 2, 2, 4] [4, 2, 3, 1] [4, 2, 3, 2] [4, 2, 3, 3] [4, 2, 3, 4] [4, 2, 4, 1] [4, 2, 4, 2] [4, 2, 4, 3] [4, 2, 4, 4] [4, 3, 1, 1] [4, 3, 1, 2] [4, 3, 1, 3] [4, 3, 1, 4] [4, 3, 2, 1] [4, 3, 2, 2] [4, 3, 2, 3] [4, 3, 2, 4] [4, 3, 3, 1] [4, 3, 3, 2] [4, 3, 3, 3] [4, 3, 3, 4] [4, 3, 4, 1] [4, 3, 4, 2] [4, 3, 4, 3] [4, 3, 4, 4] [4, 4, 1, 1] [4, 4, 1, 2] [4, 4, 1, 3] [4, 4, 1, 4] [4, 4, 2, 1] [4, 4, 2, 2] [4, 4, 2, 3] [4, 4, 2, 4] [4, 4, 3, 1] [4, 4, 3, 2] [4, 4, 3, 3] [4, 4, 3, 4] [4, 4, 4, 1] [4, 4, 4, 2] [4, 4, 4, 3] [4, 4, 4, 4]
第二个问题:
同理, 问题来了,这时候有点排列组合的意思了,1,2,3,4排列要的到的是
1 2 3 4
1 2 4 3
1 3 4 2
1 3 2 4
......
4 2 1 2
4 3 2 1
有没有发现要的到排列的情况,这里stack里的元素是1,2,3,4都不能重复
那么我在入栈的时候加个判断,如果比如1,已经在stack里面了,就不加进去,就不会得到 1 1 1 1 ...的情况了,就得到了排列
import java.util.Stack;
public class Main {
public static Stack<Integer> stack = new Stack<Integer>();
public static void main(String[] args) {
int shu[] = {1,2,3,4};
f(shu,4,0);
}
/**
*
* @param shu 待选择的数组
* @param targ 要选择多少个次
* @param cur 当前选择的是第几次
*/
private static void f(int[] shu, int targ, int cur) {
// TODO Auto-generated method stub
if(cur == targ) {
System.out.println(stack);
return;
}
for(int i=0;i<shu.length;i++) {
if(!stack.contains(shu[i])) {
stack.add(shu[i]);
f(shu, targ, cur+1);
stack.pop();
}
}
}
}
输出:
[1, 2, 3, 4] [1, 2, 4, 3] [1, 3, 2, 4] [1, 3, 4, 2] [1, 4, 2, 3] [1, 4, 3, 2] [2, 1, 3, 4] [2, 1, 4, 3] [2, 3, 1, 4] [2, 3, 4, 1] [2, 4, 1, 3] [2, 4, 3, 1] [3, 1, 2, 4] [3, 1, 4, 2] [3, 2, 1, 4] [3, 2, 4, 1] [3, 4, 1, 2] [3, 4, 2, 1] [4, 1, 2, 3] [4, 1, 3, 2] [4, 2, 1, 3] [4, 2, 3, 1] [4, 3, 1, 2] [4, 3, 2, 1]
这就是想要的排列结果了..
第三个问题:
明天待续....
原文地址: https://blog.csdn.net/Ring_k/article/details/79575533
以上是关于java实现排列组合(通俗易懂)的主要内容，如果未能解决你的问题，请参考以下文章