HDU 1166 敌兵布阵(线段树更新单节点模板)：

#include<stdio.h>
#include<string.h>
#define N 50010
int A[N];
struct node
{
    int left, right, sum;
} no[4*N]; //存放左端点，右端点，和
void Bulid(int left, int right, int root) //建立线段树
{
    int mid;
    no[root].left = left;
    no[root].right = right;
    if (left == right)
    {
        no[root].sum = A[left];
        return ;
    }
    mid = (left+right)/2;
    Bulid(left, mid, 2*root);
    Bulid(mid+1, right, 2*root+1);
    no[root].sum = no[2*root].sum + no[2*root+1].sum;
}
int Query(int left, int right, int root) //查找左端点到右端点的和
{
    int mid;
    if (no[root].left == left && no[root].right == right)
        return no[root].sum;
    mid = (no[root].left+no[root].right)/2;
    if (right <= mid)
        return Query(left, right, root*2);
    else if (left > mid)
        return Query(left, right, root*2+1);
    else
        return Query(left, mid, root*2)+Query(mid+1, right, root*2+1);
}
void Update(int k, int num, int root) //更新sum中的值
{
    if (no[root].left == no[root].right)
    {
        no[root].sum += num;
        return ;
    }
    else
    {
        no[root].sum += num;
        if (k <= no[root*2].right)
            Update(k, num, root*2);
        else
            Update(k, num, root*2+1);
    }
}
int main ()
{
    int T, n, i, L, R, Sum, num, k, ans = 0;
    char s[10];
    scanf("%d", &T);
    while (T--)
    {
        ans++;
        scanf("%d", &n);
        for (i = 1; i <= n; i++)
            scanf("%d", &A[i]);
        Bulid(1, n, 1);
        printf("Case %d:\n", ans);
        while (scanf("%s", s), strcmp(s, "End"))
        {
            if (s[0] == ‘Q‘)
            {
                scanf("%d%d", &L, &R);
                Sum = Query(L, R, 1);
                printf("%d\n", Sum);
            }
            else
            {
                scanf("%d%d", &k, &num);
                if (s[0] == ‘A‘)
                    Update(k, num, 1);
                else if (s[0] == ‘S‘)
                    Update(k, -num, 1);
            }
        }
    }
    return 0;
}