一维树状数组（HD1166）

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<string.h>
using namespace std;

#define BITMAX 50001        //数组大小
typedef int valueType;    //元素类型定义
valueType BITree[BITMAX];    //一维树状数组，初始化
/* 2^k k表示节点编号 x 二进制末尾 0 的个数 */
inline int lowbit(int x)
{
    return x & (-x);
}

/* 一维，C[x]=A[ x-lowbit(x)+1 ....... x ] */
/* 节点 x 的值增加 add */
/* x 不能为 0 ，，应该从 1 起步，否则无限循环下去 */
inline void addPoint(int x, int add, int n)
{
    for (int i = x; i <= n; i += lowbit(i)){
        BITree[i] += add;
    }
}

/* 获取前 x 项和*/
inline valueType readSum(int x)
{
    valueType sum = 0;
    for (int i = x; i > 0; i -= lowbit(i))
        sum += BITree[i];
    return sum;
}

int main()
{
    int t, n;
    char s[6];
    int a, b;
    scanf("%d", &t);
    for (int w = 1; w <= t; ++w){
        printf("Case %d:\n", w);
        scanf("%d", &n);
        memset(BITree, 0, sizeof(BITree));
        for (int i = 1; i <= n; ++i){
            scanf("%d", &a);
            addPoint(i, a, n);
        }
        while (scanf("%s",s) && s[0] != ‘E‘){
            switch (s[0])
            {
            case ‘A‘:
                scanf("%d %d", &a, &b);
                addPoint(a, b, n);
                break;
            case ‘S‘:
                scanf("%d %d", &a, &b);
                addPoint(a, -b, n);
                break;
            case ‘Q‘:
                scanf("%d %d", &a, &b);
                printf("%d\n", (readSum(b) - readSum(a - 1)));
                break;
            default:
                break;
            }
        }
    }
}