1.插入排序
void InsertSort(int *a, int n)
{
for(i = 1; i < n; i++)
{
k = a[i];
for(j = i; k < a[j-1] && j > 0; j--)
a[j] = a[j - 1];
a[j] = k;
}
}2.冒泡排序
void BubbleSort(int *a, int n)
{
for(i = 0; i < n; i++)
{
for(j = 0; j < n - i; j++)
{
if(a[j] > a[j+1])
swap(a[j], a[j+1]);
}
}
}3.选择排序
void SelectSort(int *a, int n)
{
for(i = 0; i < n-1; i++)
{
k = i;
for(j = i+1; j < n; j++)
{
if(a[j] < a[k])
k = j;
}
swap(a[i], a[k]);
}
}4.希尔排序
void ShellSort(int *a, int n)
{
int inc = n;
while(inc > 1)
{
inc = inc/3 + 1;
//插入排序排分组中元素
for(int start = 0; start < inc; start++)
{
for(i = start + inc; i < n; i += inc)
{
k = a[i];
for(j=i; k<a[j-inc]&&j>0; j-=inc)
a[j] = a[j - inc];
a[j] = k;
}
}
}
}5.基数排序
#include<queue>
void radixSort(int *a, int n, int d)
{
int digit = 1;
queue<int> digitQueue[10];
for ( i = 0; i < d; ++i) {
for (j = 0; j < n; j++)
digitQueue[(a[j] / digit) % 10].push(a[j]);
j = 0;
for (int digitVal=0; digitVal<10; ++digitVal)
while (!digitQueue[digitVal].empty())
{
a[j] = digitQueue[digitVal].front();
digitQueue[digitVal].pop();
j++;
}
cout << "number " << i << "：" << endl;
for ( j = 0; j < n; ++j)
cout << a[j] << " ";
cout << endl;
digit *= 10;//从个位数开始，直到第d位数
}
}6.堆排序（优先队列）
#define MAXN 100
class array {
private:
int elem[MAXN];
public:
int &operator[](int i) { return elem[i]; }
};
class heap {
private:
int n;
array h;
public:
void clear() { n = 0; }
int top() { return h[1]; }
int size() { return n; }
void push(int);
void pop();
};
void heap::push(int x) {//siftup
n = n + 1;
h[n] = x;
int tmp = n;
while(tmp / 2 != 0)
{
if(h[tmp/2] > h[tmp])
swap(h[tmp/2], h[tmp]);
else break;
tmp = tmp/2;
}
}
void heap::pop() {//siftdown
swap(h[1],h[n]);
n = n - 1;
i = 1;
while(2 * i <= n)
{
int parent = i, child = 2 * i;
int small = parent;
if(h[small] > h[child]) small = child;
if(child + 1 <= n && h[child+1] < h[small])
small = child + 1;
if(small == parent) break;
else
{
swap(h[parent],h[small]);
i = small;
}
}
}7.归并排序
void MergeSort(int *a, int x, int y)
// initial x = 0, y = n
{
if(y - x <= 1) return;
//Divide
int m = (y - x) / 2 + x;
//Conquer
MergeSort(a, x, m);
MergeSort(a, m, y);
//Combine
int p = x, q = m, k = 0;
int t[y - x + 1];
while( p < m || q < y)
{
if(q >= y || (p < m && a[p] <= a[q]))
t[k++] = a[p++];
else
{
t[k++] = a[q++];
//逆序对个数
//inverse_number = inverse_number + m - p;
}
}
for(p = x, k = 0; p < y; p++)
a[p] = t[k++];
}链表实现
struct linkedlist{
int data;
linkedlist *next;
};
//sort the list by mergesort and return the head of it
void Mergesort(linkedlist *&head, int len){
if(len <= 1) return;
//Divide
int m = len / 2;
linkedlist *mid = head;
linkedlist *rear = head, *new_head = NULL;
for(int i = 0; i < m ; i++)
{
mid = mid->next;
if(i == m - 2)
rear = mid;
}
rear->next = NULL;
//Conquer
Mergesort(head, m);//sort the left side
Mergesort(mid, len - m);//sort the right side
//Combine two ordered list
linkedlist *tmp1 = head, *tmp2 = mid;
linkedlist *new_rear = NULL;
while(tmp1 != NULL || tmp2 != NULL)
{
if(tmp2 == NULL ||
(tmp1 != NULL && tmp1->data <= tmp2->data))
{
if(new_head == NULL)
new_head = tmp1;
else
new_rear->next = tmp1;
new_rear = tmp1;
tmp1 = tmp1->next;
}
else
{
if(new_head == NULL)
new_head = tmp2;
else
new_rear->next = tmp2;
new_rear = tmp2;
tmp2 = tmp2->next;
}
}
head = new_head;
}8.快速排序
int partition( int *a, int low, int high )
{
int left, right;
int pivot_item = a[low];
left = low;
right = high;
while ( left < right ) {
/* Move left while item <= pivot */
while( a[left] <= pivot_item && left < high)
left++;
/* Move right while item > pivot */
while( a[right] >= pivot_item && low < right)
right--;
if ( left < right ) swap(a[left], a[right]);
}
/* right is final position for the pivot */
swap(a[low], a[right]);
return right;
}
void QuickSort(int *a, int low, int high)
{
int pivot_position;
if(low < high)
{
pivot_position = partition(a, low, high);
QuickSort(a, low, pivot_position - 1);
QuickSort(a, pivot_position + 1, high);
}
}快排思想找第k小数
int first[1000001], second[1000001];
int select(int a[], int n, int k) {
int pivot = a[0];
int st = 0, nd = 0;
for(int i = 1; i < n; i++)
{
if(a[i] <= pivot)
first[st++] = a[i];
else
second[nd++] = a[i];
}
if(st == k) return pivot;
else if(st > k) return select(first, st, k);
else return select(second, nd, k - st - 1);
}各排序算法对比（注意稳定性）
