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;
	}
}

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LeetCode | Subsets II

原文：http://blog.csdn.net/perfect8886/article/details/22922785