ACM HDU 1166 enemy soldiers ended their simple tree line intervals and seek

Topic Link http://acm.hdu.edu.cn/showproblem.php?pid=1166

AC Code

#include<iostream>
#include<string>
#include <algorithm>
#include<cstring>
#include<cstdio>
using namespace std;
typedef long long ll;
const int N = 1e5 + 5;
struct node
{
    int l,r;
    int nSum;
}tree[N*3];
int a[N];
void Build(int i, int l, int r)
{
    tree[i].l = l;
    tree[i].r = r;
    if (l == r)
    {
        tree[i].nSum = a[l];
        return;
    }
    int mid = (l+r) >> 1;
    Build(i<<1, l, mid);
    Build(i<<1|1, mid +1, r);
    tree[i].nSum = tree[i<<1].nSum + tree[i<<1|1].nSum;
}
void Add(int i, int j, int c)
{
    tree[i].nSum += c;
    if (tree[i].l == tree[i].r && tree[i].l == j)
    {
        return;
    }
    int mid = (tree[i].l + tree[i].r) >> 1;
    if (j <= mid) Add(i<<1, j,c);
    else if (j > mid) Add(i << 1|1, j ,c);

}
void Sub(int i, int j, int c)
{
    tree[i].nSum -= c;
    if (tree[i].l == tree[i].r && tree[i].l == j)
    {
        return;
    }
    int mid = (tree[i].l + tree[i].r) >> 1;
    if (j <= mid) Sub(i<<1, j,c);
    else if (j > mid) Sub(i << 1|1, j ,c);

}

int Query(int i, int a, int b)
{
    if (a == tree[i].l && b == tree[i].r)
    {
        return tree[i].nSum;
    }
    int mid = (tree[i].l + tree[i].r) >> 1;
    if (b <= mid) Query(i<<1, a, b);
    else if(a > mid) Query(i<<1|1, a, b);
    else
    {
        return Query(i<<1,a,mid)+Query(i<<1|1, mid + 1, b);
    }
}

int main()
{
    // ios::sync_with_stdio(false);cin.tie(NULL);
    int t;
    scai(t);
    for (int _  = 1; _ <= t; _++){
        printf("Case %d:\n", _);
        int n;
        scanf("%d", &n);
        for (int i = 1; i <= n; i++)
        {
            scanf("%d", &a[i]);
        }
        Build(1,1,n);
        char s[20];
        while(1){
            scanf("%s", s);
            int t1, t2;
            if (strcmp(s, "Query") == 0)
            {

                scai(t1);
                scai(t2);
                printf("%d\n", Query(1,t1,t2));
            }
            else if (strcmp(s, "Add") == 0)
            {
                scai(t1);
                scai(t2);
                Add(1,t1,t2);
            }
            else if (strcmp(s, "Sub") == 0)
            {
                scai(t1);
                scai(t2);
                Add(1,t1,-t2);
            }
            else if (strcmp(s, "End") == 0)
            {
                break;
            }
        }
    }
}