Leetcode Target sum DP solution in Kotlin

target_sum.kt

import kotlin.math.abs

// https://leetcode.com/problems/target-sum/
// dp function:  dp[i][j] = dp[i - 1][j - nums[i]] + dp[i - 1][j + nums[i]]
class TargetSum {
    fun findTargetSumWays(nums: IntArray, target: Int): Int {
        val dp = Array(nums.size + 1) { mutableMapOf<Int, Int>().withDefault { 0 } }
        dp[0][0] = 1

        for (i in 1..nums.size) {
            for (t in -abs(nums.sum())..abs(nums.sum())) {
                dp[i][t] = dp[i - 1].getValue(t - nums[i - 1]) + dp[i - 1].getValue(t + nums[i - 1])
            }
        }

        return dp[nums.size].getOrDefault(target, 0)
    }
}