codeforces打完补题

Posted 2022-12-12 newstartcy

https://codeforces.com/contest/1234/problem/D

写了个巨蠢的线段树（不愧是垃圾），有必要提醒下自己这种题怎么做

#include<iostream>
#include<cstdio>
#include<string>
#include<set>
#include<algorithm>
using namespace std;
const int maxn = 32;
set<int> st[maxn];
int main()

    string words;
    cin>>words;
    words = ‘.‘ + words;
    int len = words.size() - 1;
    for(int i=1;i<=len;++i)
        st[words[i]-‘a‘].insert(i);
    int q,cmd,pos,l,r;
    char ch;  scanf("%d",&q);
    for(int k=0;k!=q;++k)
    
        scanf("%d",&cmd);
        if(cmd==1)
        
            scanf("%d",&pos);
            getchar();
            scanf("%c",&ch);
            st[words[pos]-‘a‘].erase(pos);
            words[pos] = ch;
            st[words[pos]-‘a‘].insert(pos);
        else
            int ans = 0;
            scanf("%d%d",&l,&r);
            for(int i=0;i!=26;++i)
            
                auto it = st[i].lower_bound(l);//MDZZ 再也不直接用algorithm的二分了,容器内的快多了,佛了
                if(it == st[i].end())
                    continue;//找到大于等于l开始的字符,因为不重复,所以只需要找出一个就好了(ORZ)
                int x = *it;
                if(x <= r)
                    ++ans;
            
            cout<<ans<<‘\n‘;        
        
          

　　垃圾如我，哭啦