leetcode 216. Combination Sum III Add to List (枚举子集,限定集合大小,和为定值)

Posted by 111qqz on Thursday, April 13, 2017

TOC

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.

题意:1..9个数,从中选择k个,和为n,要求输出所有满足题意的集合。

思路:枚举子集,根据sum和集合元素个数剪枝即可。

/* ***********************************************
Author :111qqz
Created Time :2017年04月13日 星期四 15时44分56秒
File Name :216.cpp
************************************************ */
class Solution {
public:
    set<vector<int> >se;
    vector<vector<int> >res;
    int B[1005];
    void get_subset(int n,int *B,int cur,int cnt,int k,int sum,int tar)
    {
    if (cur==n)
    {
        if (cnt!=k||sum!=tar) return;
        vector<int>tmp;
        for ( int i = 0 ; i < n ; i++)
        if (B[i]) tmp.push_back(i+1);
        se.insert(tmp);
        return ;
    }
    if (cnt+1<=k&&sum+(cur+1)<=tar)
    {
        B[cur] = 1;
        get_subset(n,B,cur+1,cnt+1,k,sum+(cur+1),tar);
    }
    B[cur] = 0 ;
    get_subset(n,B,cur+1,cnt,k,sum,tar);
    }
    vector<vector<int>> combinationSum3(int k, int n) {
    get_subset(9,B,0,0,k,0,n);
    for ( auto &it : se) res.push_back(it);
    return res;
    }
};

「真诚赞赏,手留余香」

111qqz的小窝

真诚赞赏,手留余香

使用微信扫描二维码完成支付