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  • [leetcode]Combination Sum @ Python

    原题地址:https://oj.leetcode.com/problems/combination-sum/

    题意:

    Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

    The same repeated number may be chosen from C unlimited number of times.

    Note:

    • All numbers (including target) will be positive integers.
    • Elements in a combination (a1a2, … , ak) must be in non-descending order. (ie, a1 ≤ a2 ≤ … ≤ ak).
    • The solution set must not contain duplicate combinations.

    For example, given candidate set 2,3,6,7 and target 7
    A solution set is: 
    [7] 
    [2, 2, 3] 

    解题思路:穷举出符合条件的组合,我们一般考虑dfs。

    代码:

    class Solution:
        # @param candidates, a list of integers
        # @param target, integer
        # @return a list of lists of integers
        def DFS(self, candidates, target, start, valuelist):
            length = len(candidates)
            if target == 0:
                return Solution.ret.append(valuelist)
            for i in range(start, length):
                if target < candidates[i]:
                    return
                self.DFS(candidates, target - candidates[i], i, valuelist + [candidates[i]])
            
        def combinationSum(self, candidates, target):
            candidates.sort()
            Solution.ret = []
            self.DFS(candidates, target, 0, [])
            return Solution.ret
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  • 原文地址:https://www.cnblogs.com/zuoyuan/p/3777540.html
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