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78. Subsets

Python​

Package Answer​

  • Quick answer with Python built-in combinations package
from itertools import combinations


class Solution:
    def subsets(self, nums: List[int]) -> List[List[int]]:
        result = []
        for length in range(len(nums)+1):
            for comb in combinations(nums, length):
                result.append(comb)
        return result

Loop and attach​

class Solution:
    def subsets(self, nums: List[int]) -> List[List[int]]:
        result = [[]]
        for num in nums:
            result += [item+[num] for item in result]
        return result

Backtracking​

  • (TODO)

Javascript​

 var subsets = function(nums) {
   var result = [[]];
   var backtrack = function(start, max, record) {
     if (record.length === max) {
       result.push(record.slice());
       return;
     }

     for (let i = start; i < nums.length; i++) {
       record.push(nums[i])
       backtrack(i + 1, max, record);
       record.pop();
     }
   }

   for (let k = 1; k <= nums.length; k++) {
     backtrack(0, k, [])
   }
   return result;
};