LeetCode-77-Combinations

算法描述：

Given two integers n and k, return all possible combinations of k numbers out of 1 ... n.

Example:

Input: n = 4, k = 2
Output:
[[2,4],[3,4],[2,3],[1,2],[1,3],[1,4],
]

解题思路：题目要求给出所有肯能的组合，首先想到了回溯法。需要注意的是下一次迭代的起始是i+1，这样去除之前用过的数。

    vector<vector<int>> combine(int n, int k) {vector<vector<int>> results;vector<int> temp;backtracking(results, temp, n, k, 1);return results;}void backtracking(vector<vector<int>>& results, vector<int>& temp, int n, int k, int index){if(temp.size() == k){results.push_back(temp);return;}for(int i=index; i <= n; i++){temp.push_back(i);backtracking(results, temp, n , k, i+1);temp.pop_back();}}

转载于:https://www.cnblogs.com/nobodywang/p/10344792.html

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