數據結構中的排序--選擇（select）排序

選擇排序和冒泡排序不管是在算法的思路上還是代碼的實現上都差別不大。不同在於，選擇排序可以算作是冒泡排序的一種改進，這種改進主要體現在數據的移動次數上面。冒泡排序每次比較後，如果後面的元素有和比當前的元素大或者小，就會交換位置。而選擇排序，比較後是記錄當前的最小值得位置，一趟比較完成後才做交換。這樣的話，就減少了交換的次數。

選擇排序的代碼實現如下：

#include "stdafx.h"
#include <iostream>
using namespace std;

void print(int data[], int n)
{
	for (int i = 0; i < n; i++)
	{
		cout << data[i] << " ";
	}
	cout << endl;
}

void select_ascending_sort(int data[], int len)
{
	int i = 0, j = 0, temp = 0, x = 0;

	for (i = 0; i < len; i++)
	{
		temp = data[i];//temporarily store this value
		for (j = i + 1; j < len; j++)
		{
			if (temp > data[j])
			{
				temp = data[j];//save this sort fo minimum
				x = j;//save this sort of mininum number
			}
		}
		data[x] = data[i];
		data[i] = temp;
	}
}



void select_desending_sort(int data[], int len)
{
	int i = 0, j = 0, temp = 0, d = 0;

	for (i = 0; i < len; i++)
	{
		temp = data[i];
		for (j = i+1; j < len; j++)
		{
			if (temp < data[j])
			{
				temp = data[j];
				d = j;
			}
		}
		data[d] = data[i];
		data[i] = temp;
	}
}


int main()
{
	int num[] = {5,3, 7,4,3,9,6,2,10,4,3,7,1};
	int len = sizeof(num) / sizeof(int);

	cout << "data count:"<< len << ".  before sort: ";
	print(num, len);

	select_ascending_sort(num, len);
	cout << "after ascending sort: ";
	print(num, len);

	select_desending_sort(num, len);
	cout << "after desending sort: ";
	print(num, len);

	return 0;
}