56 lines
2.0 KiB
C#
56 lines
2.0 KiB
C#
/**
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* File: subset_sum_i.cs
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* Created Time: 2023-06-25
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* Author: hpstory (hpstory1024@163.com)
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*/
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namespace hello_algo.chapter_backtracking;
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public class subset_sum_i {
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/* Backtracking algorithm: Subset Sum I */
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void Backtrack(List<int> state, int target, int[] choices, int start, List<List<int>> res) {
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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.Add(new List<int>(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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for (int i = start; i < choices.Length; i++) {
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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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// Attempt: make a choice, update target, start
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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 - choices[i], choices, i, res);
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// Retract: undo the choice, restore to the previous state
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state.RemoveAt(state.Count - 1);
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}
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}
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/* Solve Subset Sum I */
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List<List<int>> SubsetSumI(int[] nums, int target) {
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List<int> state = []; // State (subset)
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Array.Sort(nums); // Sort nums
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int start = 0; // Start point for traversal
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List<List<int>> res = []; // Result list (subset list)
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Backtrack(state, target, nums, start, res);
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return res;
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}
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[Test]
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public void Test() {
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int[] nums = [3, 4, 5];
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int target = 9;
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List<List<int>> res = SubsetSumI(nums, target);
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Console.WriteLine("Input array nums = " + string.Join(", ", nums) + ", target = " + target);
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Console.WriteLine("All subsets summing to " + target + " res =");
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foreach (var subset in res) {
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PrintUtil.PrintList(subset);
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}
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}
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}
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