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// 69_QuickSort_NonRecursive.cpp : Defines the entry point for the console application.
//
/*
version: 1.0
author: hellogiser
blog: http://www.cnblogs.com/hellogiser
date: 2014/9/18
*/
#include "stdafx.h"
#include "iostream"
#include <ctime>
#include <algorithm>
#include <stack>
using namespace std;
void myswap(int &a, int &b)
{
int t = a;
a = b;
b = t;
}
void print(int *a, int n)
{
for (int i = 0; i < n; i++)
{
cout << a[i] << " ";
}
cout << endl;
}
//========================================================
// recursively
//========================================================
int partition1(int *a, int left, int right)
{
// a[left,...p-1]<=a[p]<a[p+1,...right]
int i = left;
int j = right;
int key = a[left];
while(i < j)
{
while(a[i] <= key) i++;
while(a[j] > key) j--;
if (i < j)
{
myswap(a[i], a[j]);
}
}
// left---j---i---right
myswap(a[left], a[j]);
return j;
}
int partition2(int *a, int left, int right)
{
// left, a[left+1...i]<=key, a[i+1,...j-1]>key
int i = left;
int j = left + 1;
int key = a[left];
while(j <= right)
{
if (a[j] < key)
{
i++; // so that a[i]>=key
myswap(a[i], a[j]);
}
j++;
}
//left---i---right---j
myswap(a[left], a[i]);
return i;
}
void quicksort_r(int *a, int left, int right)
{
if (left < right)
{
int p = partition1(a, left, right);
quicksort_r(a, left, p - 1);
quicksort_r(a, p + 1, right);
}
}
void QuickSort_Recursively(int *a, int n)
{
if (a == NULL || n <= 1)
return;
quicksort_r(a, 0, n - 1);
}
//========================================================
// non recursively
//========================================================
void quicksort_non_r(int *a, int left, int right)
{
// view [left,right] range as a node, which then has 2 child nodes [left,p-1] and [p+1,right] after partitioning
if (left >= right)
return;
// init stack with one range node
stack<int> s;
s.push(left);
s.push(right);
int temp_right, temp_left;
int p;
while(!s.empty())
{
temp_right = s.top();
s.pop();
temp_left = s.top();
s.pop();
if (temp_left < temp_right)
{
p = partition1(a, temp_left, temp_right);
// add node [left,p-1] and [p+1,right] to stack
s.push(temp_left);
s.push(p - 1);
s.push(p + 1);
s.push(temp_right);
}
}
}
void QuickSort_NonRecursively(int *a, int n)
{
if (a == NULL || n <= 1)
return;
quicksort_non_r(a, 0, n - 1);
}
typedef void (*fun)(int *a, int n);
void test_base(int *a, int n, fun f)
{
print(a, n);
f(a, n);
print(a, n);
cout << "==============================\n";
}
void test_recursively()
{
srand((unsigned int)time(NULL));
const int n = 10;
int a[n];
for (int i = 0; i < n; i++)
{
a[i] = rand() % 100;
}
cout << "recursively..." << endl;
test_base(a, n, QuickSort_Recursively);
}
void test_non_recursively()
{
srand((unsigned int)time(NULL));
const int n = 20;
int a[n];
for (int i = 0; i < n; i++)
{
a[i] = rand() % 100;
}
cout << "non recursively..." << endl;
test_base(a, n, QuickSort_NonRecursively);
}
void test_main()
{
test_recursively();
test_non_recursively();
}
int _tmain(int argc, _TCHAR *argv[])
{
test_main();
return 0;
}
/*
recursively...
43 5 68 83 74 12 80 61 84 48
5 12 43 48 61 68 74 80 83 84
==============================
non recursively...
43 5 68 83 74 12 80 61 84 48 67 95 57 2 17 17 98 94 17 76
2 5 12 17 17 17 43 48 57 61 67 68 74 76 80 83 84 94 95 98
==============================
*/
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