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45 lines
1.3 KiB
45 lines
1.3 KiB
/**
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* File: permutations_ii.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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/* 回溯演算法：全排列 II */
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function backtrack(state, choices, selected, res) {
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// 當狀態長度等於元素數量時，記錄解
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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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// 走訪所有選擇
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const duplicated = new Set();
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choices.forEach((choice, i) => {
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// 剪枝：不允許重複選擇元素 且 不允許重複選擇相等元素
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if (!selected[i] && !duplicated.has(choice)) {
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// 嘗試：做出選擇，更新狀態
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duplicated.add(choice); // 記錄選擇過的元素值
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selected[i] = true;
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state.push(choice);
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// 進行下一輪選擇
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backtrack(state, choices, selected, res);
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// 回退：撤銷選擇，恢復到之前的狀態
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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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/* 全排列 II */
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function permutationsII(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, 2];
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const res = permutationsII(nums);
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console.log(`輸入陣列 nums = ${JSON.stringify(nums)}`);
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console.log(`所有排列 res = ${JSON.stringify(res)}`);
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