52 lines
1.7 KiB
Swift
52 lines
1.7 KiB
Swift
/**
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* File: subset_sum_i_naive.swift
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* Created Time: 2023-07-02
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* Author: nuomi1 (nuomi1@qq.com)
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*/
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/* Backtracking algorithm: Subset Sum I */
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func backtrack(state: inout [Int], target: Int, total: Int, choices: [Int], res: inout [[Int]]) {
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// When the subset sum equals target, record the solution
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if total == target {
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res.append(state)
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return
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}
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// Traverse all choices
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for i in choices.indices {
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// Pruning: if the subset sum exceeds target, skip that choice
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if total + choices[i] > target {
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continue
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}
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// Attempt: make a choice, update elements and total
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state.append(choices[i])
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// Proceed to the next round of selection
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backtrack(state: &state, target: target, total: total + choices[i], choices: choices, res: &res)
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// Retract: undo the choice, restore to the previous state
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state.removeLast()
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}
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}
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/* Solve Subset Sum I (including duplicate subsets) */
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func subsetSumINaive(nums: [Int], target: Int) -> [[Int]] {
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var state: [Int] = [] // State (subset)
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let total = 0 // Subset sum
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var res: [[Int]] = [] // Result list (subset list)
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backtrack(state: &state, target: target, total: total, choices: nums, res: &res)
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return res
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}
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@main
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enum SubsetSumINaive {
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/* Driver Code */
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static func main() {
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let nums = [3, 4, 5]
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let target = 9
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let res = subsetSumINaive(nums: nums, target: target)
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print("Input array nums = \(nums), target = \(target)")
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print("All subsets summing to \(target) res = \(res)")
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print("Please note that the result of this method includes duplicate sets")
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}
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}
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