c++ backtracking solution, 6ms.

  • 5
    class Solution {
        bool canPartition(vector<int>& nums) {
            int sum = 0;
            for(int i =0;i<nums.size();i++){
                sum+= nums[i];
            if(sum%2) return false;
            sum /= 2;
            return helper(nums, sum, 0);
        bool helper(vector<int>& nums, int sum, int index){
            if(sum == nums[index]) return true;
            if(sum < nums[index]) return false;
            return helper(nums,sum-nums[index],index+1) || helper(nums,sum,index+1);

  • 1

    At first glance, it seems it is just naive DFS without memorization. I am actually a bit confused about why it is so fast. Am I missing something here?

  • 1

    'Cuz the posted code did very good pruning by sorting the vector in decreasing order.

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