uva 12086 树状数组

树状数组

#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <map>
#include <set>
#include <stack>
#include <vector>
#include <sstream>
#include <string>
#include <cstring>
#include <algorithm>
#include <iostream>
#define maxn 200010
#define INF 0x7fffffff
#define inf 10000000
#define ull unsigned long long
#define ll long long
using namespace std;

int a[maxn], arr[maxn];

int lowbit(int x)
{
    return x&(-x);
}

int sum(int x)
{
    int ret = 0;
    while(x > 0)
        ret += a[x], x -= lowbit(x);
    return ret;
}

void add(int x, int d)
{
    while(x < maxn)
        a[x] += d, x += lowbit(x);
}

void init()
{
    memset(arr, 0, sizeof(arr));
    memset(a, 0, sizeof(a));
}
int main()
{
    int n, ca = 1;
    while(scanf("%d", &n) == 1 && n)
    {
        init();
        for(int i = 1; i <= n; ++ i)
        {
            scanf("%d", &arr[i]);
            add(i, arr[i]);
        }
        char s[10];
        if(ca > 1) puts("");
        printf("Case %d:\n", ca++);
        while(scanf("%s", s))
        {
            if(s[0] == 'E') break;
            else if(s[0] == 'S')
            {
                int x, r;
                scanf("%d%d", &x, &r);
                add(x, r-arr[x]);
                arr[x] = r;
            }
            else
            {
                int le, ri;
                scanf("%d%d", &le, &ri);
                printf("%d\n", sum(ri) - sum(le-1));
            }
        }
    }
    return 0;
}