LeetCode-in-All

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:

Solution

class Solution {
    func canPartition(_ nums: [Int]) -> Bool {
        var sums = nums.reduce(0, +)
        if sums % 2 == 1 {
            return false
        }
        sums /= 2
        var dp = [Bool](repeating: false, count: sums + 1)
        dp[0] = true
        for num in nums {
            for sum in stride(from: sums, through: num, by: -1) {
                dp[sum] = dp[sum] || dp[sum - num]
            }
        }
        return dp[sums]
    }
}