43 lines
1.2 KiB
JavaScript
43 lines
1.2 KiB
JavaScript
/**
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* File: permutations_i.js
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* Created Time: 2023-05-13
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* Author: Justin (xiefahit@gmail.com)
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*/
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/* Backtracking algorithm: Permutation I */
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function backtrack(state, choices, selected, res) {
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// When the state length equals the number of elements, record the solution
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if (state.length === choices.length) {
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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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choices.forEach((choice, 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, 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.pop();
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}
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});
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}
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/* Permutation I */
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function permutationsI(nums) {
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const res = [];
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backtrack([], nums, Array(nums.length).fill(false), res);
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return res;
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}
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// Driver Code
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const nums = [1, 2, 3];
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const res = permutationsI(nums);
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console.log(`输入数组 nums = ${JSON.stringify(nums)}`);
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console.log(`所有排列 res = ${JSON.stringify(res)}`);
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