排序板子（基数，归并）

基数排序（栈模拟）

首先离散化，然后二进制从低位到高位看每位是否为1，为1放进b栈，否则放入c栈，然后将b,c栈的数顺次放入a栈，循环直到最高位。

#include <bits/stdc++.h>
typedef long long ll;
// #define DEBUG freopen("_in.txt", "r", stdin)
#define DEBUG freopen("_in.txt", "r", stdin), freopen("_out.txt", "w", stdout);
using namespace std;
const ll INF = 0x3f3f3f3f3f3f3f3f;
const int maxn = 1e3 + 10;
const int maxm = 2e4 + 10;

ll n;
ll arr[maxn],brr[maxn],crr[maxn],ans[4][maxm],tot;
pair<ll,ll> pa[maxn];

void add(ll sta,ll stb)
{
    
    
    ans[1][++tot]=sta;
    ans[2][tot]=stb;
}

int main()
{
    
    
    // DEBUG;
    scanf("%lld", &n);
    for(ll i=1;i<=n;i++)
    {
    
    
        ll v;
        scanf("%lld", &v);
        pa[i]=make_pair(v,i);
    }
    sort(pa+1,pa+n+1);
    for(ll i=1;i<=n;i++)
    {
    
    
        arr[pa[i].second]=i;
    }
    ll sia,sib,sic;
    for(ll i=0;i<10;i++)
    {
    
    
        sia=sib=sic=0;
        for(ll j=n;j>=1;j--)
        {
    
    
            if((arr[j]>>i)&1)
            {
    
    
                brr[++sib]=arr[j];
                add(1,2);
            }
            else
            {
    
    
                crr[++sic]=arr[j];
                add(1,3);
            }
        }
        for(ll j=sib;j>=1;j--)
        {
    
    
            arr[++sia]=brr[j];
            add(2,1);
        }
        for(ll j=sic;j>=1;j--)
        {
    
    
            arr[++sia]=crr[j];
            add(3,1);
        }
    }
    printf("%lld\n",tot);
    for(ll i=1;i<=tot;i++)
    {
    
    
        printf("%lld %lld\n",ans[1][i],ans[2][i]);
    }
}

归并排序

void update(int now)
{
    
    
    Size[now] = Size[now * 2] + Size[now * 2 + 1];
}

void dfs(int L, int R, int now)
{
    
    
    if (L == R)
    {
    
    
        Size[now] = 1;
        return;
    }
    dfs(L, mid, now * 2);
    for (int i = 1; i <= Size[now * 2]; i++)
        stack_2[++top_2] = stack_1[top_1--], ans_1[++ans] = 1, ans_2[ans] = 2;
    dfs(mid + 1, R, now * 2 + 1);
    for (int i = 1; i <= Size[now * 2 + 1]; i++)
        stack_3[++top_3] = stack_1[top_1--], ans_1[++ans] = 1, ans_2[ans] = 3;
    int cnt_2 = 0, cnt_3 = 0;
    while (cnt_2 < Size[now * 2] && cnt_3 < Size[now * 2 + 1])
    {
    
    
        if (stack_2[top_2] >= stack_3[top_3])
            stack_1[++top_1] = stack_2[top_2--], ans_1[++ans] = 2, ans_2[ans] = 1, cnt_2++;
        else
            stack_1[++top_1] = stack_3[top_3--], ans_1[++ans] = 3, ans_2[ans] = 1, cnt_3++;
    }
    while (cnt_2 < Size[now * 2])
        stack_1[++top_1] = stack_2[top_2--], ans_1[++ans] = 2, ans_2[ans] = 1, cnt_2++;
    while (cnt_3 < Size[now * 2 + 1])
        stack_1[++top_1] = stack_3[top_3--], ans_1[++ans] = 3, ans_2[ans] = 1, cnt_3++;
    update(now);
}

归并排序

//归并排序
#include<bits/stdc++.h>
using namespace std;
#define N 1000005
int a[N] ,b[N];//b为辅助数组
void merge_sort(int l , int r)
{
    
    
    if(r-l > 0)//如果整个区间中元素个数大于1，则继续分割
    {
    
    
        int mid = (l+r) / 2 ;
        int i = l; //辅助数组的下标
        int p = l , q = mid+1;
        merge_sort(l , mid);
        merge_sort(mid+1 , r);
        //printf("%d-%d  %d-%d\n",p,mid ,q ,r);
        while(p<=mid || q<=r)//左右两部分只要有一部分不为空
        {
    
    
            if(q>r || (p<=mid && a[p]<=a[q]))//从左半数组复制到辅助数组
                b[i++] = a[p++];
            else b[i++] = a[q++];//从右半数组复制到辅助数组
        }
        for(i = l ; i <= r; i++)//将b中排好序的元素复制到a中
            a[i] = b[i];
    }
}
int main()
{
    
    
    int n;
    while(cin >> n)
    {
    
    
        for(int i = 1 ; i <= n; i ++)
            cin >> a[i];
        merge_sort(1 , n);
        for(int i = 1; i <= n; i++)
            cout << a[i] << " ";
        cout << endl;
    }
    return 0;
}