leetcode 046 Permutations

最新推荐文章于 2019-04-18 10:32:12 发布

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本文介绍了一种生成给定数字集合所有可能排列的算法实现。通过C++代码详细展示了如何找出一个整数序列的所有排列组合，并提供了具体示例，如[1,2,3]的全排列。

Given a collection of distinct numbers, return all possible permutations.

For example,
[1,2,3] have the following permutations:
[1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1].

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class Solution {
public:
    bool generateNext(vector<int> &nums) {
		int len = nums.size(), i=0, j=0;

		for(i=len-2; i >= 0; i--) {
			if(nums[i] < nums[i+1]) break;
		}

		if(i < 0) return false;

		for(j = len-1; j >= i; j--) {
			if(nums[j] > nums[i]) break;
		}

		int temp = nums[j];
		nums[j] = nums[i];
		nums[i] = temp;

		for(int l = i+1, r = len-1; l < r; l++, r--) {
			temp = nums[r];
			nums[r] = nums[l];
			nums[l] = temp;
		}

		return true;
	}
	vector<vector<int> > permute(vector<int> &nums) {
		sort(nums.begin(), nums.end());
		vector<vector<int> > ans;

		ans.push_back(nums);

		while(generateNext(nums)) {
			ans.push_back(nums);
		}

		return ans;
	}
};