LeetCode 39. Combination Sum

Leetcode 39. Combination Sum --数组元素组合,和为目标值,一个元素可用无数次,输出每种组合,每种组合唯一 Given asetof candidate numbers (candidates)(without duplicates)and a target number (target), find all unique combinations incandidateswhere the candidate numbers sums totarget. Thesamerepeat... 阅读详情

ti题目链接:

题目链接:https://leetcode.com/problems/combination-sum/ 

 用给定数组中的数组成target,每个数可以用无限次

dfs,每一层遍历该层的数字最多能使用的次数(可以使用0次,也就是不选这个数)。这样可以保证不会重复,而且每个数字都能用到。

class Solution {
    List<List<Integer>> ans = new ArrayList<>();
    int []nums = new int [30];
    int n;
    public List<List<Integer>> combinationSum(int[] candidates, int target) {
        n = candidates.length;
        nums = candidates;
        int []cnt = new int [30];
        dfs(0,cnt,0,target);
        return ans;
    }
    public void dfs(int ind,int[] cnt,int sum,int target){
        if(sum == target){
            ArrayList<Integer> tem = new ArrayList<Integer>();
            for(int i=0;i<n;i++)
                for(int j = 0;j<cnt[i];j++)
                    tem.add(nums[i]);
            ans.add(tem);
            return;
        }
        if(ind>=n)
            return;
        for(int j=0;sum + j*nums[ind]<=target;j++){
            cnt[ind]=j;
            dfs(ind+1,cnt,sum + j*nums[ind],target);
            cnt[ind]=0;
        }
    }
}

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Leetcode39:Combination Sum

题目:给定一个整型数组candidates,和一个目标值target,使用数组中的数组成target,找出所有的组合。例如: candidates = {2,3,6,7}; target =7 ; 则返回的结果为:[[7],[2,2,3]] 。 题目说明,candidates中的数字全为正数,target也全为正数。 并且返回的结果中candidates中的数可以是重复的,而且不限次数的重复。但每

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leetcode记录39.Combination Sum

39.Combination Sum √ Accepted √ 168/168 cases passed (20 ms) √ Your runtime beats 59.36 % of cpp submissions √ Your memory usage beats 49.71 % of cpp submissions (11.2 MB) /* * @lc app=leetco...

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