虽然此题卡了珂朵莉树，也不应该是 WA 21?

#include<set>
#include<cstdio>
#include<iostream>
#include<cstring>
using namespace std;
#define It set<odt>::iterator
#define ll long long
struct odt
{
    ll l,r;
    mutable ll val;
    bool operator <(const odt &n)const
    {
        return l<n.l;
    }
    odt(ll a,ll b,ll c)
    {
        l=a,r=b,val=c;
    }
    odt(ll a)
    {
        l=a;
    }
};
set<odt> tree;
It split(ll x)
{
    It it=tree.lower_bound(x);
    if(it!=tree.end()&&it->l==x)
    return it;
    it--;
    ll l=it->l,r=it->r,val=it->val;
    tree.erase(it);
    tree.insert(odt(l,x-1,val));
    return tree.insert(odt(x,r,val)).first;
}
void assign(ll l,ll r,ll val)
{
    It it2=split(r+1),it1=split(l);
    tree.erase(it1,it2);
    tree.insert(odt(l,r,val));
}
ll time_k(ll l,ll r,ll k)
{
    It it2=split(r+1),it1=split(l);
    ll ans=0;
    for(It it=it1;it!=it2;it++)
    {
        if(it->val==k)
        ans+=it->r-it->l+1;
    }
    return ans;
}
void Sort(ll l,ll r)
{
    It it2=split(r+1),it1=split(l);
    ll k=l;
    int bucket[125];
    memset(bucket,0,sizeof(bucket));
    for(It it=it1;it!=it2;it++)
    {
        bucket[it->val]+=it->r-it->l+1;
//      cout<<it->l<<" "<<it->r<<endl;
    }
    tree.erase(it1,it2);
    for(int i='A';i<='Z';++i)
    {
        tree.insert(odt(k,k+bucket[i]-1,i));
        k+=bucket[i];
    }
}
int n,m;
int main()
{
    scanf("%d%d",&n,&m);
    scanf("\n");
    for(int i=1;i<=n;++i)
    {
        char a=getchar();
        if(a>'Z')
            a=a-'a'+'A';
        tree.insert(odt(i,i,a));
    }
    for(int i=1;i<=m;++i)
    {
        int op,x,y;
        char k;
        scanf("%d%d%d",&op,&x,&y);
        if(op<=2)
        {
            getchar();
            k=getchar();
            if(k>'Z')
                k=k-'a'+'A';
        }
        if(op==1)
        {
            printf("%lld\n",time_k(x,y,k));
        }
        else if(op==2)
        {
            assign(x,y,k);
        }
        else
        {
            Sort(x,y);
        }
    }
    return 0;
}