Dynamic programming exercise - Build a necklace with the greatest value without surpassing the maximum allowed weight (modification of the 0/1 knapsack problem)

Necklace.swift

import Foundation

func max(a: Int, b: Int) -> Int {
    return a > b ? a : b
}

func necklace(pearls: [[Int]]) -> [[Int]] {
    var res = Array.init(repeating: Array.init(repeating: 0, count: 151), count: pearls.count)
    var ret: [[Int]] = []
    
    for i in 0...150 {
        let weight = pearls[0][0]
        let value  = pearls[0][1]
        res[0][i]  = weight <= i ? value : 0
    }
    
    for i in 1...pearls.count - 1 {
        for j in pearls[i][0]...150 {
            let weight = pearls[i][0]
            let value  = pearls[i][1]
            res[i][j]  = max(res[i - 1][j], res[i - 1][j - weight] + value)
        }
    }
    
    var i = pearls.count - 1
    var j = 150
    
    while i >= 0 && j >= 0 {
        if i > 0 {
            let mayorQueArriba = res[i][j] > res[i - 1][j]
            
            if mayorQueArriba {
                ret.append(pearls[i])
                j = j - pearls[i][0]
                i = i - 1
            } else {
                i = i - 1
            }
        } else {
            if res[i][j] == 0 {
                break
            } else {
                ret.append(pearls[i])
                j = j - pearls[i][0]
            }
        }
    }
    
    return ret
}

let cnt = Int.random(in: 0...150)
var pearls: [[Int]] = Array.init(repeating: Array.init(repeating: 0, count: 2), count: cnt)

for i in 0...pearls.count - 1 {
    pearls[i][0] = Int.random(in: 0...25)
    pearls[i][1] = Int.random(in: 1...500)
}

necklace(pearls: pearls)