2025/1/24

今天学了st表，以及线段树

#include<bits/stdc++.h>
#define ll long long
#define par pair<ll,ll>
#define prr pair<ll,par>
#define st first
#define nd second
#define ld long double
#define MX 1000000000000ll
#define MO 1000000007ll
// #define MO 998244353ll
#define MN 0.000001
#define MXM 2000002
#define MXN 1000002
#define PP 131ll
#define LG 20
using namespace std;
inline void rd(ll &x){x=0;short f=1;char c=getchar();while((c<'0'||c>'9')&&c!='-') c=getchar();if(c=='-') f=-1,c=getchar();while(c>='0'&&c<='9') x=x*10+c-'0',c=getchar();x*=f;}
inline void pt(ll x){if(x<0) putchar('-'),x=-x;if(x>9) pt(x/10);putchar(x%10+'0');}
/*
BBBBBBB  ZZZZZZZZ MM         MM
BB    BB      ZZ  MMM       MMM
BB    BB     ZZ   MMMM     MMMM
BBBBBBB     ZZ    MM MM   MM MM
BB    BB   ZZ     MM  MM MM  MM
BB    BB  ZZ      MM   MMM   MM
BBBBBBB  ZZZZZZZZ MM    M    MM
*/
ll T=1,n,q,a[MXN],s[MXN],ans;
ll st[MXN][LG],nl;
ll ask(ll l,ll r){
    if(l>r) return -MX;
    ll x=log2(r-l+1);
    return max(st[l][x],st[r-(1<<x)+1][x]);
}
void solve(){
    rd(n),rd(q);
    nl=log2(n);
    for(ll i=1;i<=n;i++)
        rd(a[i]),s[i]=s[i-1]+a[i],st[i][0]=a[i]-s[i-1];
    for(ll k=1;k<=nl;k++)
        for(ll i=1;i+(1<<(k-1))<=n;i++)
            st[i][k]=max(st[i][k-1],st[i+(1<<(k-1))][k-1]);
    while(q--){
        ll l,r;
        rd(l),rd(r);
        pt(max(0ll,ask(l+1,r)+s[l-1])),puts("");
    }
}int main(){while(T--) solve();}