c ++ to implement common algorithm

Sorting Algorithm

Bubble sort, merge sort, insertion sort, selection sort, quick sort

Quick sort:

1. Take the left sentinel first element, looking forward from the rear, is larger than the element, immobile; smaller than that of the element, transposition
2. Sentinel on the left and right than most, less than transposition find sentinel
3. transposition sentinel on the right, and the left side, to find sentinel greater than
4. the left sentinel than their larger than the right side thereof is small; the two sides each made fast row
demo.cpp

int partition(int *pArr, int arrLen, int low, int high)
{
	int standarVal = pArr[low];
	while (low < high)
	{
		while (low < high&& pArr[high] >= standarVal)
		{//最右边元素比标准值要大时，保持循环，
			high--;
		}
		if (low < high)//如果比标准值大时换位
		{
			int tmp = pArr[low];
			pArr[low] = pArr[high];
			pArr[high] = tmp;
		}
		printArray(pArr, arrLen);
		while (low < high&& pArr[low] <= standarVal)
		{//最左边元素比标准值要小时，保持循环，
			low++;
		}
		if (low < high)//如果比标准值大时换位
		{
			int tmp = pArr[low];
			pArr[low] = pArr[high];
			pArr[high] = tmp;
		}
		printArray(pArr, arrLen);
	}
	return low; //返回中间值
}
bool quickSortImpl(int *pArr, int arrLen,int low,int high)
{
	printf("\nlow = %d, high = %d\n", low, high);
	if (low < high)
	{
		//第一步：找到中间值    负责排序的函数
		int centerPoint = partition(pArr, arrLen, low, high);
		printf("\ncenterPoint =  %d\n", centerPoint);
		//第二步：前半部分排序
		quickSortImpl(pArr, arrLen, low, centerPoint - 1);

		//第三步：后半部分排序
		quickSortImpl(pArr, arrLen, centerPoint + 1, high);
	}
	return true;
}
bool quickSort(int *pArr, int arrLen, int *pTar)
{
	if (!pArr || !pTar)
	{
		return false;
	}
	for (int i = 0; i < arrLen; i++)
	{
		pTar[i] = pArr[i];
	}
	quickSortImpl(pTar, arrLen, 0, arrLen - 1);
	return true;
}

Merging Sort

Adjacent to the first set of pairwise sequencing, two adjacent rows after sorting, sequentially drained

Bubble sort

demp.cpp

/*
冒泡排序法
*/  
#include <cstdlib>
#include <iostream>
using namespace std;
void printArray(int *pArr, int n)
{
	for (int j = 0; j < n; j++)
	{
		cout << pArr[j] << " ";
	}
	cout << endl;
}
bool bubbleSort(int *pArr, int arrLen, int *pTar)
{
	if (!pArr || !pTar)
	{
		return false;
	}
	for (int i = 0; i < arrLen; i++)
	{
		pTar[i] = pArr[i];
	} 
	for (int i = 0; i < arrLen - 1; i++) //最后一个不用排
	{
		for(int j = 0;j < arrLen - i - 1;j++)
		{
			if (pTar[j] > pTar[j + 1])
			{
				int temp = pTar[j];
				pTar[j] = pTar[j + 1];
				pTar[j + 1] = temp;
			}
			
		}
		printArray(pTar, arrLen);
	}
	return true;
}

int main(void)
{
	int arr[5] = { 6,5,4,3,2 };
	int tar[5] = { 0 };

	printArray(arr, 5);
	bubbleSort(arr, 5, tar);
	//printArray(tar, 5);
	system("pause");
	return 0;
}

Insertion Sort

demo.cpp

bool insertSort(int *pArr, int arrLen, int *pTar)
{
	if (!pArr || !pTar)
	{
		return false;
	}
	for (int i = 0; i < arrLen; i++)
	{
		pTar[i] = pArr[i];
	}
	//一共要排n-1次
	for (int i = 0; i < arrLen - 1; i++)
	{
		//每次选一个哨兵 i+1   第0个元素不用插入
		//如果哨兵比前面相邻的元素大，就不用排序，直接插入
		if (pTar[i] > pTar[i + 1]) 
		{
			int x = pTar[i + 1]; //x为哨兵
			int j = i;
			while (x < pTar[j]) //找到合适的位置
			{
				pTar[j + 1] = pTar[j]; //该元素向后移动一位
				j--;
				if (j < 0) //防止插在第一个位置时，循环不能终止
				{
					break;
				}
			}
			//出来时,j+1,哨兵不能把比他小的值覆盖，索引要向前移动一位
			pTar[j + 1] = x;
		}
		printArray(pTar, arrLen);
	}

	return true;
}

Select sort method

demo.cpp

//在指定的集合中找出最小索引  from（含）,to(不含)
int selectMinKey(int *pArr, int from, int to)
{
	int k = from; //存放最小值的索引
	for (int i = from + 1; i < to; i++)
	{
		if (pArr[k] > pArr[i])
		{
			k = i;
		}
	}
	return k;
}

bool selectSort(int *pArr, int arrLen, int *pTar)
{
	if (!pArr || !pTar)
	{
		return false;
	}
	for (int i = 0; i < arrLen; i++)
	{
		pTar[i] = pArr[i];
	}
	for (int i = 0; i < arrLen; i++)
	{
		int key = selectMinKey(pTar, i, arrLen); // 找到最小值
		if (key != i)
		{
			//交换位置
			int tmp = pTar[i];
			pTar[i] = pTar[key];
			pTar[key] = tmp;
		}
		printArray(pTar, arrLen);
	
	}
	return true;
}