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归并排序.cpp
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归并排序.cpp
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#include<stdio.h>
#include<iostream>
#include<bits/stdc++.h>
#include<algorithm>
using namespace std;
void printArr(vector<int> & nums){
for(auto e:nums){
cout<<e<<' ';
}
cout<<endl;
}
void mergeOp(vector<int> & arr,int low,int mid,int high){
// 这里可以再优化复制的区域,减少时间。
vector<int> arrCopy(arr);
// 合并两个数列
int i,j,index;
for(i=low,j=mid+1,index=low ; i<=mid&&j<=high ; index++){
if(arrCopy[i]<arrCopy[j]){
arr[index] = arrCopy[i++];
}else{
arr[index] = arrCopy[j++];
}
}
if(i<=mid){
for(int k=i ; k<=mid ; k++){
arr[index++] = arrCopy[k];
}
}else{
for(int k=j ; k<=high ; k++){
arr[index++] = arrCopy[k];
}
}
}
void mergeOp_plus(vector<int> & arr,int low,int mid,int high){
// 优化代码。
vector<int> arrCopy;
// 合并两个数列,用vector存储需要改变的数。
int i=low,j=mid+1,index=low;
while(i <= mid && j <= high){
if(arr[i] > arr[j])
arrCopy.push_back(arr[j++]);
else
arrCopy.push_back(arr[i++]);
}
while(i <= mid)
arrCopy.push_back(arr[i++]);
while(j <= high)
arrCopy.push_back(arr[j++]);
for(int i : arrCopy)
arr[index++] = i;
}
void mergeSort(vector<int> & arr,int low,int high){
if(low<high){
int mid = low+(high-low)/2;
mergeSort(arr,low,mid);
mergeSort(arr,mid+1,high);
mergeOp_plus(arr,low,mid,high);
printArr(arr);
}
}
int main(){
vector<int> nums1 = {10,9,8,7,6,5,4,3,2,1};
printArr(nums1);
mergeSort(nums1,0,nums1.size()-1);
cout<<"--------------"<<endl;
printArr(nums1);
return 0;
}