A+B Problem题解（太难了）

这题我们需要使用树状数组来完成，记得开long long，代码如下：

// by 1145141919810
#include <iostream>
using namespace std;
long long tr[3];
int lowbit(int x) {
    return x & -x;
}
void add(int x, int val) {
    for (int i = x; i <= 2; i += lowbit(i)) tr[i] += val;
}
long long query(int x) {
    long long sum = 0;
    for (int i = x; i >= 1; i -= lowbit(i)) sum += tr[i];
    return sum;
}
int main() {
    int v;
    for (int i = 1; i <= 2; i++) {
        cin >> v;
        add(i, v);
    }
    cout << query(2);
    return 0;
}
// by 1145141919810