Submission #1315749

#	Time	Username	Problem	Language	Result	Execution time	Memory
1315749		kokokai	Election (BOI18_election)	C++20	100 / 100	763 ms	141840 KiB

election

#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define fi first
#define se second
const int N = 5e5+5;
const int LG = 20;
int spt[N][LG],mnval[N][LG];
int mnr[N][LG];
int lg2[N];
int a[N],pre[N],suf[N],nxt[N];
int n,q;
int getmin(int l,int r){
    if(l>r) return 1e9;
    int lg=lg2[r-l+1];
    return min(mnr[l][lg],mnr[r-(1<<lg)+1][lg]);
}
signed main(){
    ios::sync_with_stdio(false);cin.tie(nullptr);
    if(fopen("text.inp","r")){
        freopen("text.inp","r",stdin);
    }
    cin>>n;
    lg2[1]=0;
    for(int i=2;i<=n;i++) lg2[i]=lg2[i/2]+1;
    for(int i=1;i<=n;i++){
        char c;
        cin>>c;
        if(c == 'C') a[i]=1;
        else a[i]=-1;
        pre[i]=pre[i-1]+a[i];
    }
    for(int i=n;i>=1;i--) suf[i]=suf[i+1]+a[i];
    for(int i=1;i<=n;i++) mnr[i][0]=suf[i];
    for(int lg=1;lg<LG;lg++){
        for(int i=1;i+(1<<lg)-1<=n;i++){
            mnr[i][lg] = min(mnr[i][lg-1],mnr[i+(1<<(lg-1))][lg-1]);
        }
    }
    map<int,int> mp;
    for(int lg=0;lg<LG;lg++) spt[n+1][lg]=n+1;
    for(int i=n;i>=1;i--){
        mp[pre[i]]=i;
        if(mp.find(pre[i]-1) != mp.end()){
            spt[i][0]=mp[pre[i]-1];
            mnval[i][0]=getmin(i+1,spt[i][0]-1);
            if(mnval[i][0] != 1e9) mnval[i][0]++;
        }else{
            spt[i][0]=n+1;
            mnval[i][0]=1e9;
        }
        if(mp.find(pre[i-1]-1) != mp.end()){
            nxt[i]=mp[pre[i-1]-1];
        }else nxt[i]=n+1;
    }
    for(int lg=1;lg<LG;lg++){
        for(int i=1;i<=n;i++){
            if(spt[i][lg-1] != n+1){
                spt[i][lg]=spt[spt[i][lg-1]][lg-1];
                mnval[i][lg] = min(mnval[spt[i][lg-1]][lg-1],mnval[i][lg-1] + (1<<(lg-1)));
            }else{
                spt[i][lg]=n+1;
                mnval[i][lg]=1e9;
            }
        }
    }
    cin>>q;
    while(q--){
        int l,r;
        cin>>l>>r;
        int p=l;
        int ans=0;
        int sum=0;
        int mn=1e9;
        p=nxt[p];
        for(int lg=LG-1;lg>=0;lg--){
            if(spt[p][lg] <= r){
                sum += (1<<lg);
                p=spt[p][lg];
            }
        }
        p=nxt[l];
        if(nxt[l] <= r){
            sum++;
            ans++;
        }
        for(int lg=LG-1;lg>=0;lg--){
            if(spt[p][lg] <= r){
                ans += (1<<lg);
                mn=min(mn,mnval[p][lg] + sum-ans);
                p=spt[p][lg];
            }
        }
        //cerr<<nxt[l]<<'\n';
        mn = min(mn,getmin(l,min(r,nxt[l]-1))+sum);
        mn = min(mn,getmin(p+1,r));
        mn -= suf[r+1];
        if(mn < 0) ans += -mn;
        cout<<ans<<'\n';
    }
}

Compilation message (stderr)

election.cpp: In function 'int main()':
election.cpp:21:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   21 |         freopen("text.inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 28 / 28
• Subtask 2: 54 / 54
• Subtask 3: 18 / 18