Segment Tree (No Lazy)

/*
Paradeigma tou Segment Tree:
Otan pianei to athrisma twn stoixeiwn
Kai otan ginete update prosthetei kapio sigkekrimeno arithmo stis theseis
Liga logia gia avto:
To segment tree einai ena binary tree data strucure pou o kathe "komvos"
apothikevkei mia geniki timi gia to interval pou einai ipevthino
diladi an apothikevoume athrismata(paradeigma mas) tote o "komvos" pou en ipevthinos gia
tin perioxi 1-8 xerei to athrisma twn stoixeiwn apo to 1 ws to 8
Avto petyxenete apo to oti pernei tin pliroforia apo ta paidia tou(binary tree)
opou to arsistero paidi eshi p tin arxi ws tin mesi (dld apothikevei to athrisma p to 1 ws 4)
kai to dexi paidi eshi p tin mesi+1(gia na men iparxoun colisions) ws to telos(dld apothikevei to athrisma p to 5 ws 8)
alla an einai fyllo dld exei tin pliroforia gia ena stoixeio aplos pianoume tin pliroforia p ton pinaka mas
ston kodika einai: seg[cth]=pin[s];
*/
#include<iostream>

using namespace std;

int pin[100000];///Pinakas me to data
int seg[200010];///To segment tree mas
int n;///To plithos twn stoixeiwn

///To recurence relation
int rec(int a, int b)
{
    ///Edw tha grafoume tin sxesi tou patera me ta paidia tou
    ///Sigkekrimena to pateras einai to athrisma twn 2 paidiwn
    ///Tha mporouse na einai to pio megalo apo ta 2
    ///tote tha stelname:
    ///return max(a, b);
    return a+b;
}

///Gia arxikopoiisi tou Segment Tree
///s=>arxi t interval
///e=>telos t inetrval
///cth=> pou eimaste sto Segment Tree
void reset(int s, int e, int cth)
{
    ///Leaf Periptosi
    if(s==e)///Otan I arxi en ison tou telous
    {
        seg[cth]=0; ///midenizoume
        return; ///klinoume to maxazi
    }

    ///Oxi Leaf Periptosi
    int mid=(s+e)/2;///Vriskoume to middle

    reset(s, mid, cth*2);///pame sto aristero paidi
    reset(mid+1, e, cth*2+1);///pame sto dexi paidi

    ///To recurence relation!!!(stelnoume ta 2 paithkia)
    seg[cth]=rec(seg[cth*2], seg[cth*2+1]);

    return;///klinoume to maxazi
}

///Gia na dwsoume times sto Segment Tree
///s=>arxi t interval
///e=>telos t inetrval
///cth=>pou eimaste sto Segment Tree
void create(int s, int e, int cth)
{
    ///Leaf Periptosi
    if(s==e)///Otan I arxi en ison tou telous
    {
        seg[cth]=pin[s];///Dioume stin akrea periptosi tin timi
        return;
    }

    int mid=(s+e)/2;///Vriskoume to middle

    create(s, mid, cth*2);///pame sto aristero paidi
    create(mid+1, e, cth*2+1);///pame sto dexi paidi

    ///To recurence relation!!!(stelnoume ta 2 paithkia)
    seg[cth]=rec(seg[cth*2], seg[cth*2+1]);

    return;
}

///Otan theloume na antlisoume plirofories apo to segment tree
///ters=>arxi avtoy p theloume
///tere=>telos avtoy p theloume
///s=>arxi t interval
///e=>telos t inetrval
///cth=>pou eimaste sto Segment Tree
int query(int ters, int tere, int s, int e, int cth)
{
    ///an fkoume ektos oriwn
    if(tere<s || ters>e)
    {
        ///epistrefoume mia timi pou den tha mas epireasei
        ///px sto athrisma to 0
        return 0;
    }

    ///an o "komvos" en mes sta oreia mas
    if(ters<=s && e<=tere)
    {
        ///aplos stelnoume tin timi
        return seg[cth];
    }

    int mid=(s+e)/2;///Vriskoume to middle

    ///Pianoume pliroforia apo to aristero paidi
    int part1=query(ters, tere, s, mid, cth*2);

    ///Pianoume pliroforia apo to dexi paidi
    int part2=query(ters, tere, mid+1, e, cth*2+1);

    ///Epistrefoume to recurence relation
    return rec(part1, part2);
}

///Otan theloume na ananeosoume plirofories apo to segment tree
///Edw aplos prosthetoume to num sta stoixeia
///ters=>arxi avtoy p theloume
///tere=>telos avtoy p theloume
///s=>arxi t interval
///e=>telos t inetrval
///num=>timi alagis
///cth=>pou eimaste sto Segment Tree
void updall(int ters, int tere, int s, int e, int num, int cth)
{
    ///an fkoume ektos oriwn
    if(tere<s || ters>e)
    {
        ///klinoume to maxazi
        return;
    }

    ///otan ftasoume se fyllo
    if(s==e)
    {
        ///aplos prothetoume
        seg[cth]+=num;
        ///klinoume to maxazi
        return;
    }

    int mid=(s+e)/2;///Vriskoume to middle

    ///kanoume update to aristero paidi
    updall(ters, tere, s, mid, num, cth*2);
    ///kanoume update to dexi paidi
    updall(ters, tere, mid+1, e, num, cth*2+1);

    ///To recurence relation!!!(stelnoume ta 2 paithkia)
    seg[cth]=rec(seg[cth*2], seg[cth*2+1]);

    return;///klinoume to maxazi
}

///Ena paradeigma pws doulefkoun ta Functions
int main()
{

    int i;///Gia to for
    cin>>n;///Diavazoume ta stoixeia
    reset(1, n, 1);///midenizoume to segment tree
    ///diavazoume ta stoixeia
    for(i=1; i<=n; i++)
        cin>>pin[i];
    ///diavazoume ta stoixeia

    ///Dimiourgoume to segment tree
    create(1, n, 1);

    ///Typwnw to athrisma twn stoixeiwn 1->n
    cout<<query(1, n, 1, n, 1)<<"\n";

    ///Mexri tin mesi proisthetw 15 se kathe stoixeio
    updall(1, n/2, 1, n, 15, 1);

    ///kai thorw tin mageia pou egine ;)
    cout<<query(1, n, 1, n, 1)<<"\n";

    return 0;
}