hdu1166 敌兵布阵 【线段树】

题目链接：​​http://acm.hdu.edu.cn/showproblem.php?pid=1166​​​
题意：中文题
解析：线段树，单点更新，单点查询

#include <bits/stdc++.h>
using namespace std;
const int maxn = 50000+100;
struct node
{
    int l,r;
    int sum;
}tree[4* maxn];
int a[maxn];
void push_up(int i)
{
    tree[i].sum = tree[i<<1].sum + tree[i<<1|1].sum;
}
void build(int i,int l,int r)
{
    tree[i].l = l,tree[i].r = r;
    tree[i].sum = 0;
    if(l==r)
    {
        tree[i].sum = a[l];
        return ;
    }
    int mid = (l+r)>>1;
    build(i<<1,l,mid);
    build(i<<1|1,mid+1,r);
    push_up(i);
}
void update(int i,int pos,int val)
{
    int l = tree[i].l;
    int r = tree[i].r;
    if(l==pos && r==pos)
    {
        tree[i].sum += val;
        return ;
    }
    int mid = (l+r)>>1;
    if(mid>=pos)
        update(i<<1,pos,val);
    else
        update(i<<1|1,pos,val);
    push_up(i);
}
int query(int i,int l,int r)
{
    int L = tree[i].l;
    int R = tree[i].r;
    if(l<=L && R<=r)
        return tree[i].sum;
    int mid = (L+R)>>1;
    int ans = 0;
    if(mid<r)
        ans += query(i<<1|1,l,r);
    if(mid>=l)
        ans += query(i<<1,l,r);
    return ans;
}
int main(void)
{
    int t,case_t = 1;
    cin>>t;
    while(t--)
    {
        int n;
        scanf("%d",&n);
        for(int i=1;i<=n;i++)
            scanf("%d",&a[i]);
        build(1,1,n);
        char op[100];
        printf("Case %d:\n",case_t++);
        while(~scanf("%s",op) && op[0]!='E')
        {
            int x,y;
            scanf("%d %d",&x,&y);
            if(op[0]=='Q')
                printf("%d\n",query(1,x,y));
            else if(op[0]=='A')
                update(1,x,y);
            else
                update(1,x,-y);
        }
    }
    return 0;
}