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47 lines
1.1 KiB
JavaScript
47 lines
1.1 KiB
JavaScript
/**
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* File: two_sum.js
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* Created Time: 2022-12-15
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* Author: gyt95 (gytkwan@gmail.com)
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*/
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/* 方法 1：総当たり列挙 */
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function twoSumBruteForce(nums, target) {
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const n = nums.length;
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// 2重ループのため、時間計算量は O(n^2)
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for (let i = 0; i < n; i++) {
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for (let j = i + 1; j < n; j++) {
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if (nums[i] + nums[j] === target) {
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return [i, j];
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}
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}
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}
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return [];
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}
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/* 方法 2：補助ハッシュテーブル */
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function twoSumHashTable(nums, target) {
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// 補助ハッシュテーブルを使用し、空間計算量は O(n)
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let m = {};
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// 単一ループで、時間計算量は O(n)
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for (let i = 0; i < nums.length; i++) {
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if (m[target - nums[i]] !== undefined) {
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return [m[target - nums[i]], i];
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} else {
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m[nums[i]] = i;
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}
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}
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return [];
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}
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/* Driver Code */
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// 方法 1
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const nums = [2, 7, 11, 15],
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target = 13;
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let res = twoSumBruteForce(nums, target);
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console.log('方法1 res = ', res);
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// 方法 2
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res = twoSumHashTable(nums, target);
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console.log('方法2 res = ', res);
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