47 lines
1.4 KiB
Rust
47 lines
1.4 KiB
Rust
/*
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* File: permutations_i.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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/* Backtracking algorithm: Permutation I */
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fn backtrack(mut state: Vec<i32>, choices: &[i32], selected: &mut [bool], res: &mut Vec<Vec<i32>>) {
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// When the state length equals the number of elements, record the solution
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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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// Traverse all choices
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for i in 0..choices.len() {
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let choice = choices[i];
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// Pruning: do not allow repeated selection of elements
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if !selected[i] {
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// Attempt: make a choice, update the state
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selected[i] = true;
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state.push(choice);
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// Proceed to the next round of selection
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backtrack(state.clone(), 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.remove(state.len() - 1);
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}
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}
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}
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/* Permutation I */
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fn permutations_i(nums: &mut [i32]) -> Vec<Vec<i32>> {
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let mut res = Vec::new(); // State (subset)
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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, 3];
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let res = permutations_i(&mut nums);
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println!("Input array nums = {:?}", &nums);
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println!("All permutations res = {:?}", &res);
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}
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