Leetcode 216. Combination Sum III

triplebee

发布于 2018-01-12 14:45:06

4700

发布于 2018-01-12 14:45:06

Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers.

Example 1:

Input: k = 3, n = 7

Output:

[[1,2,4]]

Example 2:

Input: k = 3, n = 9

Output:

[[1,2,6], [1,3,5], [2,3,4]]

给定一个数字，求用1-9的数字求和得到这个数的不同组合。

dfs，一路从leetcode刷过来这也不是什么难事。

class Solution {
public:
    void dfs(int k, int now, int n, int sum, vector<vector<int>> &res, vector<int> path)
    {
        if(sum > n) return ;
        if(k == 0)
        {
            if(sum == n) res.push_back(path);
            return ;
        }
        if(now == 0) return ;
        for(int i = now; i > 0; i--)
        {
            vector<int> tmp = path;
            tmp.push_back(i);
            dfs(k-1, i - 1, n, sum + i, res, tmp);
        }
    }
    vector<vector<int>> combinationSum3(int k, int n) {
        vector<vector<int>> res;
        vector<int> path;
        dfs(k, 9, n, 0, res, path);
        return res;
    }
};

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原始发表：2017-03-23 ，如有侵权请联系 cloudcommunity@tencent.com 删除

dfs