s0416_partition_equal_subset_sum

416. Partition Equal Subset Sum

Medium

Given a non-empty array nums containing only positive integers, find if the array can be partitioned into two subsets such that the sum of elements in both subsets is equal.

Example 1:

Input: nums = [1,5,11,5]

Output: true

Explanation: The array can be partitioned as [1, 5, 5] and [11].

Example 2:

Input: nums = [1,2,3,5]

Output: false

Explanation: The array cannot be partitioned into equal sum subsets.

Constraints:

• 1 <= nums.length <= 200
• 1 <= nums[i] <= 100

Solution

class Solution {
  bool canPartition(List<int> nums) {
    int sums = nums.reduce((a, b) => a + b);

    if (sums % 2 == 1) {
      return false;
    }

    sums ~/= 2; // Integer division
    List<bool> dp = List.filled(sums + 1, false);
    dp[0] = true;

    for (int num in nums) {
      for (int sum = sums; sum >= num; sum--) {
        dp[sum] = dp[sum] || dp[sum - num];
      }
    }

    return dp[sums];
  }
}