LeetCode | Subsets II

题目

Given a collection of integers that might contain duplicates, S, return all possible subsets.

Note:

Elements in a subset must be in non-descending order.
The solution set must not contain duplicate subsets.

For example,

If S = 

[1,2,2]

, a solution
is:

[
[2],
[1],
[1,2,2],
[2,2],
[1,2],
[]
]

分析

在Subsets解法1基础上进行修改，当出现重复元素时，要在上一重复元素的作用范围外添加当前重复元素，避免重复子集的出现。

代码

import java.util.ArrayList;
import java.util.Arrays;

public class SubsetsII {
public ArrayList<ArrayList<Integer>> subsetsWithDup(int[] num) {
Arrays.sort(num);
ArrayList<ArrayList<Integer>> results = new ArrayList<ArrayList<Integer>>();
ArrayList<Integer> list = new ArrayList<Integer>();
results.add(list);
int preSize = 0;
for (int i = 0; i < num.length; ++i) {
int cutPoint = 0;
if (i > 0 && num[i] == num[i - 1]) {
cutPoint = preSize;
}
int j = results.size() - 1;
preSize = results.size();
while (j >= cutPoint) {
list = new ArrayList<Integer>(results.get(j--));
list.add(num[i]);
results.add(list);
}
}
return results;
}
}