55 lines
1.7 KiB
Kotlin
55 lines
1.7 KiB
Kotlin
/**
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* File: subset_sum_i_native.kt
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* Created Time: 2024-01-25
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* Author: curtishd (1023632660@qq.com)
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*/
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package chapter_backtracking.subset_sum_i_naive
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/* Backtracking algorithm: Subset Sum I */
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fun backtrack(
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state: MutableList<Int>,
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target: Int,
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total: Int,
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choices: IntArray,
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res: MutableList<MutableList<Int>?>
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) {
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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.add(state.toMutableList())
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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.add(choices[i])
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// Proceed to the next round of selection
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backtrack(state, target, total + choices[i], choices, res)
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// Retract: undo the choice, restore to the previous state
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state.removeAt(state.size - 1)
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}
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}
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/* Solve Subset Sum I (including duplicate subsets) */
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fun subsetSumINaive(nums: IntArray, target: Int): MutableList<MutableList<Int>?> {
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val state = mutableListOf<Int>() // State (subset)
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val total = 0 // Subset sum
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val res = mutableListOf<MutableList<Int>?>() // Result list (subset list)
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backtrack(state, target, total, nums, res)
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return res
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}
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/* Driver Code */
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fun main() {
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val nums = intArrayOf(3, 4, 5)
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val target = 9
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val res = subsetSumINaive(nums, target)
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println("Input array nums = ${nums.contentToString()}, target = $target")
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println("All subsets equal to $target res = $res")
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println("Please note that the result of this method includes duplicate sets")
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} |