42 lines
1.3 KiB
Go
42 lines
1.3 KiB
Go
// File: permutations_ii.go
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// Created Time: 2023-05-14
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// Author: Reanon (793584285@qq.com)
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package chapter_backtracking
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/* Backtracking algorithm: Permutation II */
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func backtrackII(state *[]int, choices *[]int, selected *[]bool, res *[][]int) {
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// When the state length equals the number of elements, record the solution
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if len(*state) == len(*choices) {
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newState := append([]int{}, *state...)
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*res = append(*res, newState)
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}
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// Traverse all choices
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duplicated := make(map[int]struct{}, 0)
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for i := 0; i < len(*choices); i++ {
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choice := (*choices)[i]
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// Pruning: do not allow repeated selection of elements and do not allow repeated selection of equal elements
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if _, ok := duplicated[choice]; !ok && !(*selected)[i] {
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// Attempt: make a choice, update the state
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// Record selected element values
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duplicated[choice] = struct{}{}
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(*selected)[i] = true
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*state = append(*state, choice)
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// Proceed to the next round of selection
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backtrackII(state, choices, selected, res)
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// Retract: undo the choice, restore to the previous state
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(*selected)[i] = false
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*state = (*state)[:len(*state)-1]
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}
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}
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}
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/* Permutation II */
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func permutationsII(nums []int) [][]int {
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res := make([][]int, 0)
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state := make([]int, 0)
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selected := make([]bool, len(nums))
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backtrackII(&state, &nums, &selected, &res)
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return res
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}
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