leetcode: Combinations

最新推荐文章于 2019-01-13 06:57:22 发布

原创最新推荐文章于 2019-01-13 06:57:22 发布 · 1k 阅读

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本文详细介绍了如何通过递归算法从1到n的整数中选取k个数，并生成所有可能的组合。通过实例演示了组合的生成过程，包括实现步骤和代码解析。

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

For example,
If n = 4 and k = 2, a solution is:

[
  [2,4],
  [3,4],
  [2,3],
  [1,2],
  [1,3],
  [1,4],
]

class Solution {
public:

    void foo(int th_num, int n, int remain, std::vector<int> &curVector, std::vector<std::vector<int>> &returnVector)
    {
        
        if (remain == 0)
        {
            returnVector.push_back(curVector);
            return;
        }
        
        for (int i = th_num; i <= n; i++)
        {
            curVector.push_back(i);
            foo(i+1, n, remain-1, curVector, returnVector);
            curVector.pop_back();
        }
    }

    vector<vector<int> > combine(int n, int k) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function 
        
        
        std::vector<int> curVector;
        std::vector<vector<int>> returnVector;
        
        if (k == 0)
            return returnVector;
            
        
        for (int i = 1; i <= n; i++)
        {
            
            curVector.push_back(i);
            foo(i+1, n, k-1, curVector, returnVector);
            curVector.pop_back();
            
        }
        
    }
};