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49 lines
1.3 KiB
49 lines
1.3 KiB
/**
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* File: two_sum.kt
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* Created Time: 2024-01-25
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* Author: curtishd (1023632660@qq.com)
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*/
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package chapter_searching
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/* 方法一：暴力枚举 */
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fun twoSumBruteForce(nums: IntArray, target: Int): IntArray {
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val size = nums.size
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// 两层循环，时间复杂度为 O(n^2)
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for (i in 0..<size - 1) {
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for (j in i + 1..<size) {
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if (nums[i] + nums[j] == target) return intArrayOf(i, j)
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}
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}
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return IntArray(0)
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}
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/* 方法二：辅助哈希表 */
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fun twoSumHashTable(nums: IntArray, target: Int): IntArray {
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val size = nums.size
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// 辅助哈希表，空间复杂度为 O(n)
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val dic = HashMap<Int, Int>()
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// 单层循环，时间复杂度为 O(n)
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for (i in 0..<size) {
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if (dic.containsKey(target - nums[i])) {
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return intArrayOf(dic[target - nums[i]]!!, i)
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}
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dic[nums[i]] = i
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}
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return IntArray(0)
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}
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/* Driver Code */
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fun main() {
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// ======= Test Case =======
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val nums = intArrayOf(2, 7, 11, 15)
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val target = 13
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// ====== Driver Code ======
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// 方法一
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var res = twoSumBruteForce(nums, target)
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println("方法一 res = ${res.contentToString()}")
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// 方法二
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res = twoSumHashTable(nums, target)
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println("方法二 res = ${res.contentToString()}")
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} |