树状数组，适用于单点修改，区间查询

Posted 2021-03-07 king-of-dark

int c[50005]; //对应原数组和树状数组
int lowbit(int x){
    return x&(-x);
}

void updata(int i,int k){    //在i位置加上k
    while(i <= n){
        c[i] += k;
        i += lowbit(i);
    }
}

int getsum(int i){        //求A[1 - i]的和
    int res = 0;
    while(i > 0){
        res += c[i];
        i -= lowbit(i);
    }
    return res;
}