59 lines
1.7 KiB
C++
59 lines
1.7 KiB
C++
/**
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* File: merge_sort.cpp
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* Created Time: 2022-11-25
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* Author: krahets (krahets@163.com)
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*/
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#include "../utils/common.hpp"
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/* 合并左子数组和右子数组 */
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void merge(vector<int> &nums, int left, int mid, int right) {
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// 左子数组区间为 [left, mid], 右子数组区间为 [mid+1, right]
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// 创建一个临时数组 tmp ，用于存放合并后的结果
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vector<int> tmp(right - left + 1);
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// 初始化左子数组和右子数组的起始索引
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int i = left, j = mid + 1, k = 0;
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// 当左右子数组都还有元素时，进行比较并将较小的元素复制到临时数组中
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while (i <= mid && j <= right) {
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if (nums[i] <= nums[j])
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tmp[k++] = nums[i++];
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else
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tmp[k++] = nums[j++];
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}
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// 将左子数组和右子数组的剩余元素复制到临时数组中
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while (i <= mid) {
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tmp[k++] = nums[i++];
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}
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while (j <= right) {
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tmp[k++] = nums[j++];
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}
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// 将临时数组 tmp 中的元素复制回原数组 nums 的对应区间
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for (k = 0; k < tmp.size(); k++) {
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nums[left + k] = tmp[k];
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}
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}
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/* 归并排序 */
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void mergeSort(vector<int> &nums, int left, int right) {
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// 终止条件
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if (left >= right)
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return; // 当子数组长度为 1 时终止递归
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// 划分阶段
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int mid = (left + right) / 2; // 计算中点
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mergeSort(nums, left, mid); // 递归左子数组
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mergeSort(nums, mid + 1, right); // 递归右子数组
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// 合并阶段
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merge(nums, left, mid, right);
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}
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/* Driver Code */
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int main() {
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/* 归并排序 */
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vector<int> nums = {7, 3, 2, 6, 0, 1, 5, 4};
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mergeSort(nums, 0, nums.size() - 1);
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cout << "归并排序完成后 nums = ";
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printVector(nums);
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return 0;
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}
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