线段树单点更新

#include<bits/stdc++.h>

using namespace std;

#define lson l, mid, root << 1
#define rson mid + 1, r, root << 1 | 1
const int maxn = 50005;
int sum[maxn << 2];
int t,n;
char op[10];

void PushUp(int root){
    sum[root] = sum[root << 1] + sum[root << 1 | 1];
}
void build(int l,int r,int root)
{
    if(l == r){
        scanf("%d",&sum[root]);
        return;
    }
    int mid = (l + r) >> 1;
    build(lson);build(rson);
    PushUp(root);
}
void update(int pos,int add,int l,int r,int root)
{
    if(l == r){
        sum[root] += add;
        return;
    }
    int mid = (l + r) >> 1;
    if(pos <= mid) update(pos,add,lson);
    else update(pos,add,rson);
    PushUp(root);
}
int query(int L,int R,int l,int r,int root)
{
    if(L <= l && r <= R){
        return sum[root];
    }
    int mid = (l + r) >> 1;
    int ret = 0;
    if(L <= mid) ret += query(L,R,lson);
    if(R > mid) ret += query(L,R,rson);
    return ret;
}
int main()
{
    scanf("%d",&t);
    for(int cas = 1; cas <= t; cas++)
    {
        scanf("%d",&n);
        build(1,n,1);
        printf("Case %d:\n",cas);
        while(~scanf("%s",op))
        {
            if(op[0] == ‘E‘) break;
            int a,b;
            scanf("%d%d",&a,&b);
            if(op[0] == ‘Q‘){
                printf("%d\n",query(a,b,1,n,1));
            }
            else if(op[0] == ‘S‘){
                update(a,-b,1,n,1);
            }
            else{
                update(a,b,1,n,1);
            }
        }
    }
    return 0;
}