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quicksort.cpp
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quicksort.cpp
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#include <vector>
#include <iostream>
using namespace std;
void quicksort(vector<int>& arr, int start, int end);
int partition(vector<int>& arr, int start, int end);
void myswap(vector<int>& arr, int i, int j);
int main(int argc, char const *argv[]) {
int a[11] = {1,3,4,2,6,3,7,8,5,13,10};
vector<int> arr(a, a + 11);
quicksort(arr, 0, arr.size() - 1);
for(int i = 0; i != arr.size(); i ++){
cout << arr[i] << " ";
}
cout << endl;
return 0;
}
void quicksort(vector<int>& arr, int start, int end){
if(start >= end){
return;
} else{
int pivot = partition(arr, start, end);
quicksort(arr, start, pivot - 1);
quicksort(arr, pivot + 1, end);
}
}
int partition(vector<int>& arr, int start, int end){
int mid = start + (end - start)/2;
if(arr[start] > arr[mid]){
myswap(arr, start, mid);
}
if(arr[start] > arr[end]){
myswap(arr, start, end);
}
if(arr[mid] > arr[end]){
myswap(arr, mid, end);
}
myswap(arr, mid, end - 1);
if(end - start < 3){
return mid;
}
int pivot = arr[end - 1];
int i = start + 1;
int j = end - 2;
while(i < j){
while(pivot > arr[i]){
i ++;
}
while(pivot < arr[j]){
j --;
}
if(i < j){
myswap(arr, i, j);
}
}
myswap(arr, i, end - 1);
return i;
}
void myswap(vector<int>& arr, int i, int j){
int temp = arr[j];
arr[j] = arr[i];
arr[i] = temp;
}