[LeetCode] Permutations II

最新推荐文章于 2019-05-11 19:52:40 发布

HQBUPT

最新推荐文章于 2019-05-11 19:52:40 发布

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分类专栏： LeetCode 文章标签： LeetCode 刷题

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本文介绍了一种使用递归生成整数数组中不重复排列的方法。通过排序数组并逐个插入最后一个元素到所有可能的位置，可以生成所有不重复的排列。

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vector<vector<int> > permuteUnique(vector<int> &num) {	
	vector<vector<int>> permutations;
	if (num.size() <= 1)
	{
		permutations.push_back(num);
		return permutations;
	}
	sort(num.begin(), num.end());
	int lastNum = num.back();
	num.pop_back();
	vector<vector<int>> permutationsWithoutLastNum = permuteUnique(num);
	for (int i = 0; i < permutationsWithoutLastNum.size(); i++)
	{
		vector<int> permutationWithoutLastNum = permutationsWithoutLastNum[i];
		int lastSame = permutationWithoutLastNum.size()-1;
		for (; lastSame >= 0; lastSame--)
		{
			if (permutationWithoutLastNum[lastSame] == lastNum)
			{
				break;
			}
		}
		for (int j = lastSame+1; j < permutationWithoutLastNum.size(); j++)
		{
			vector<int> permutation = permutationWithoutLastNum;
			//if (permutation[j] != lastNum)
			{
				permutation.insert(permutation.begin()+j, lastNum);
				permutations.push_back(permutation);
			}
		}
		vector<int> permutation = permutationWithoutLastNum;
		permutation.push_back(lastNum);
		permutations.push_back(permutation);
	}
	return permutations;    
}