62 lines
2.0 KiB
Rust
62 lines
2.0 KiB
Rust
/*
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* File: subset_sum_ii.rs
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* Created Time: 2023-07-09
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* Author: codingonion (coderonion@gmail.com)
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*/
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/* Backtracking algorithm: Subset Sum II */
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fn backtrack(
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mut state: Vec<i32>,
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target: i32,
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choices: &[i32],
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start: usize,
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res: &mut Vec<Vec<i32>>,
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) {
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// When the subset sum equals target, record the solution
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if target == 0 {
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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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// Pruning two: start traversing from start to avoid generating duplicate subsets
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// Pruning three: start traversing from start to avoid repeatedly selecting the same element
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for i in start..choices.len() {
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// Pruning one: if the subset sum exceeds target, end the loop immediately
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// This is because the array is sorted, and later elements are larger, so the subset sum will definitely exceed target
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if target - choices[i] < 0 {
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break;
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}
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// Pruning four: if the element equals the left element, it indicates that the search branch is repeated, skip it
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if i > start && choices[i] == choices[i - 1] {
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continue;
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}
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// Attempt: make a choice, update target, start
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state.push(choices[i]);
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// Proceed to the next round of selection
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backtrack(state.clone(), target - choices[i], choices, i, res);
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// Retract: undo the choice, restore to the previous state
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state.pop();
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}
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}
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/* Solve Subset Sum II */
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fn subset_sum_ii(nums: &mut [i32], target: i32) -> Vec<Vec<i32>> {
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let state = Vec::new(); // State (subset)
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nums.sort(); // Sort nums
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let start = 0; // Start point for traversal
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let mut res = Vec::new(); // Result list (subset list)
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backtrack(state, target, nums, start, &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 = [4, 4, 5];
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let target = 9;
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let res = subset_sum_ii(&mut nums, target);
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println!("Input array nums = {:?}, target = {}", &nums, target);
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println!("All subsets equal to {} res = {:?}", target, &res);
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}
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