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51 lines
1.5 KiB
51 lines
1.5 KiB
/*
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* File: permutations_ii.rs
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* Created Time: 2023-07-15
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* Author: codingonion (coderonion@gmail.com)
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*/
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use std::collections::HashSet;
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/* 回溯演算法：全排列 II */
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fn backtrack(mut state: Vec<i32>, choices: &[i32], selected: &mut [bool], res: &mut Vec<Vec<i32>>) {
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// 當狀態長度等於元素數量時，記錄解
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if state.len() == choices.len() {
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res.push(state);
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return;
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}
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// 走訪所有選擇
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let mut duplicated = HashSet::<i32>::new();
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for i in 0..choices.len() {
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let choice = choices[i];
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// 剪枝：不允許重複選擇元素 且 不允許重複選擇相等元素
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if !selected[i] && !duplicated.contains(&choice) {
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// 嘗試：做出選擇，更新狀態
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duplicated.insert(choice); // 記錄選擇過的元素值
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selected[i] = true;
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state.push(choice);
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// 進行下一輪選擇
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backtrack(state.clone(), choices, selected, res);
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// 回退：撤銷選擇，恢復到之前的狀態
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selected[i] = false;
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state.pop();
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}
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}
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}
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/* 全排列 II */
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fn permutations_ii(nums: &mut [i32]) -> Vec<Vec<i32>> {
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let mut res = Vec::new();
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backtrack(Vec::new(), nums, &mut vec![false; nums.len()], &mut res);
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res
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}
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/* Driver Code */
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pub fn main() {
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let mut nums = [1, 2, 2];
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let res = permutations_ii(&mut nums);
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println!("輸入陣列 nums = {:?}", &nums);
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println!("所有排列 res = {:?}", &res);
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}
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