Data Structure-segment tree (c + +)

Source:

#include <cstdio>
int m,n,num (0), h[100001];
struct Treetype
{
int left,right,lefts,rights,sum;//In this code, the semi-open half-closed interval is applied.
}i[200020]; The number of nodes of a complete binary tree is applied.
void x1 (int t1,int T2)//achievements.
{
int t=++num;//Note that in the line segment tree, always follow the left small right large principle.
i[t].left=t1;
i[t].right=t2;
if (t1!=t2-1)
{
i[t].lefts=num+1;//using the left small right large principle, numbering.
X1 (T1, (T1+T2)/2);
i[t].rights=num+1;
X1 ((T1+T2)/2,t2);//Note that this is a half-open half-closed interval.
i[t].sum=i[i[t].lefts].sum+i[i[t].rights].sum;//use backtracking to make intervals and updates.
}
Else
I[T].SUM=H[T1];
}
void x2 (int t,int x,int y)//modified.
{
if (i[t].left==i[t].right-1)//Note, this is a half-open half-closed interval.
i[t].sum+=y;
Else
{
if (x< (i[t].left+i[t].right)/2)//Use dichotomy to modify the node.
x2 (i[t].lefts,x,y);
if (x>= (i[t].left+i[t].right)/2)//Note that this is a half-open half-closed interval.
x2 (i[t].rights,x,y);
i[t].sum=i[i[t].lefts].sum+i[i[t].rights].sum;//use backtracking to make intervals and updates.
}
}
int x3 (int t,int x,int y)//sum.
{
if (x<=i[t].left&&y>=i[t].right)//At this time, the desired interval contains this interval.
return i[t].sum;
int ans (0);
if (x< (i[t].left+i[t].right)/2)//separates the desired interval.
ans+=x3 (i[t].lefts,x,y);
if (y> (i[t].left+i[t].right)/2)
ans+=x3 (i[t].rights,x,y);
return ans;
}
int main ()
{
scanf ("%d", &n);
for (int a=1;a<=n;a++)
scanf ("%d", &h[a]);
X1 (1,n+1);//Note that this is a half-open half-closed interval.
scanf ("%d", &m);
for (int a=1;a<=m;a++)
{
int x, y, Z;
scanf ("%d%d%d", &x,&y,&z);
if (x==1)
x2 (1,y,z);
Else
printf ("%d\n", X3 (1,y,z+1));//Note that this is a half-open half-closed interval.
}
return 0;
}

Data Structure-segment tree (c + +)