why O2 RE?
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why O2 RE?
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_Icetihw_楼主2024/12/12 17:28
#include<bits/stdc++.h>
#define ll long long
using namespace std;
ll lowbit(ll x){return x&-x;}
ll tr[200005][2];
ll n,y[200005];
ll l[200005],r[200005];//左边小于y[i],右边大于y[i]
ll update(ll x,ll c){
    while(x <= n){
        tr[x][c]++;
        x += lowbit(x);
    }
}
ll query(ll x,ll c){
    ll ans = 0;
    while(x){
        ans += tr[x][c];
        x -= lowbit(x);
    }
    return ans;
}
int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    cin>>n;
    for(int i=1;i<=n;i++) cin>>y[i];
    for(int i=1;i<=n;i++){
        l[i] = query(y[i],0);
        update(y[i],0);
    }
    for(int i=n;i>=1;i--){
        r[i] = query(n - y[i] + 1,1);
        update(n - y[i] + 1,1);
    }
    ll ans1 = 0 , ans2 = 0;
    for(int i=1;i<=n;i++){
        ans1 += (i - 1 - l[i]) * r[i];
        ans2 += l[i] * (n - i - r[i]);
    }
    cout<<ans1<<" "<<ans2<<endl;
    return 0;
}

萌新刚学OI,不懂为什么开O2 RE,关O2 T,说的数组越界,thxthx

2024/12/12 17:28
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