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Posts tagged as “combination”

花花酱 LeetCode 216. Combination Sum III

题目大意:输出所有用k个数的和为n的组合。可以使用的元素是1到9。

Problem:

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:

Example 2:

Input: k = 3, n = 9

Output:

 



Idea:

DFS + backtracking

bit

Solution:

C++

 

C++ / binary

 

Python

 

 

Related problems:

花花酱 LeetCode 40. Combination Sum II

Problem:

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

Each number in C may only be used once in the combination.

Note:

  • All numbers (including target) will be positive integers.
  • The solution set must not contain duplicate combinations.

For example, given candidate set [10, 1, 2, 7, 6, 1, 5] and target 8,
A solution set is:

 



Idea:

DFS

Solution:

C++ / set

 

C++ / vector

 

花花酱 LeetCode 39. Combination Sum

Problem:

Given a set of candidate numbers (C(without duplicates) 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.
  • The solution set must not contain duplicate combinations.

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

 

Idea:

DFS

Solution: C++

 

Python

 

花花酱 Leetcode 140. Word Break II

Problem

Given a non-empty string s and a dictionary wordDict containing a list of non-empty words, add spaces in s to construct a sentence where each word is a valid dictionary word. You may assume the dictionary does not contain duplicate words.

Return all such possible sentences.

For example, given
s = "catsanddog",
dict = ["cat", "cats", "and", "sand", "dog"].

A solution is ["cats and dog", "cat sand dog"].

UPDATE (2017/1/4):
The wordDict parameter had been changed to a list of strings (instead of a set of strings). Please reload the code definition to get the latest changes.

Solution

Time complexity: O(2^n)

Space complexity: O(2^n)

C++

Python3

 

Related Problems