排序算法（快排，归并，堆排，冒泡，选择，插入）

以下算法均按从小到大排序。

1、快排

#include 
using namespace std;

void QuikSort(int a[], int l, int r){
    if(l >= r) return;
    int key = a[l];
    int i = l, j = r;
    while(i < j){
        while(i < j && a[j] > key) j--;
        while(i < j && a[i] <= key) i++;
        if(i < j) swap(a[i], a[j]);
    }
    swap(a[l], a[j]);
    QuikSort(a, l, j);
    QuikSort(a, j+1, r);
}
int main(){
    // int a[] = {19,5,3,674,84,85,4,90,6,34};
    // int a[] = {9,8,7,6,5,4,3,2,1};
    // int a[] = {1,2,3,4,5,6,7,8,9};
    int a[] = {5,4,6,1,7,8,2,3,9};
    int n = 9;
    QuikSort(a, 0, n-1);
    for(int i = 0; i < n; i++)
        cout<

2、归并

#include 
#include 
using namespace std;

void MergeSort(int a[], int l, int r){
    if(l == r) return;
    int mid = (l+r) >> 1;
    MergeSort(a, l, mid);
    MergeSort(a, mid+1, r);
    vector tmp;
    int i = l, j = mid+1;
    while(i <= mid && j <= r){
        if(a[i] <= a[j]) tmp.push_back(a[i++]);
        else tmp.push_back(a[j++]);
    }
    while(i <= mid) tmp.push_back(a[i++]);
    while(j <= r) tmp.push_back(a[j++]);
    for(int k = 0; k < tmp.size(); k++)
        a[l++] = tmp[k];
}
int main(){
    // int a[] = {19,5,3,674,84,85,4,90,6,34};
    // int a[] = {9,8,7,6,5,4,3,2,1};
    // int a[] = {1,2,3,4,5,6,7,8,9};
    int a[] = {5,4,6,1,7,8,2,3,9};
    int n = 9;
    MergeSort(a, 0, n-1);
    for(int i = 0; i < n; i++)
        cout<

3、堆排

注意：为了用数组方便模拟建树，将数组下标从1开始

#include 
#include 
using namespace std;

void HeapAdjust(int a[], int idx, int mx){
    int val = a[idx];
    for(int j = 2*idx; j <= mx; j*=2){
        if(j < mx && a[j] < a[j+1]) j++;
        if(val > a[j]) break;;
        a[idx] = a[j], idx = j;
    }
    a[idx] = val;
}
void HeapSort(int a[], int n){
    if(n <= 1) return;
    for(int i = n>>1; i >= 1; i--){
        HeapAdjust(a, i, n);
    }
    for(int i = n; i >=1; i--){
        swap(a[i], a[1]);
        HeapAdjust(a, 1, i-1);
    }
}
int main(){
    // int a[] = {0,19,5,3,674,84,85,4,90,6,34};
    // int a[] = {0,9,8,7,6,5,4,3,2,1};
    // int a[] = {0,1,2,3,4,5,6,7,8,9};
    int a[] = {0,5,4,6,1,7,8,2,3,9};
    int n = 9;
    HeapSort(a, n);
    for(int i = 1; i <= n; i++)
        cout<

4、冒泡

void BubbleSort(int a[], int n){
    for(int i = 1; i < n; i++){
        int flag = false;
        for(int j = 0; j < n-i; j++){
            if(a[j] > a[j+1]){
                swap(a[j], a[j+1]);
                flag = true;
            }
        }
        if(!flag)break;
    }
}

5、选择

void SelectionSort(int a[], int n){
    for(int i = 0; i < n-1; i++){
        int idx = i;
        for(int j = i+1; j < n; j++){
            if(a[idx] > a[j])
                idx = j;
        }
        swap(a[idx], a[i]);
    }
}

6、插入

void InsertionSort(int a[], int n){
    for(int i = 1; i < n; i++){
        int tmp = a[i];
        int j = i-1;
        while(j >= 0 && tmp < a[j]){
            a[j+1] = a[j];
            j--;
        }
        a[j+1] = tmp;
    }
}