52 lines
1.9 KiB
JavaScript
52 lines
1.9 KiB
JavaScript
/**
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* File: subset_sum_ii.js
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* Created Time: 2023-07-30
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* Author: yuan0221 (yl1452491917@gmail.com)
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*/
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/* Backtracking algorithm: Subset Sum II */
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function backtrack(state, target, choices, start, 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.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 (let 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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// 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, target - choices[i], choices, i + 1, 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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function subsetSumII(nums, target) {
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const state = []; // State (subset)
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nums.sort((a, b) => a - b); // Sort nums
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const start = 0; // Start point for traversal
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const 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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/* Driver Code */
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const nums = [4, 4, 5];
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const target = 9;
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const res = subsetSumII(nums, target);
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console.log(`输入数组 nums = ${JSON.stringify(nums)}, target = ${target}`);
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console.log(`所有和等于 ${target} 的子集 res = ${JSON.stringify(res)}`);
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