一半RE求调

#include <bits/stdc++.h>
using namespace std;
int b[500010],n;
struct Node{
    int aa,ai;
    bool operator < (const Node& rhs) const {
    	return (this->aa < rhs.aa) || (this->aa == rhs.aa && this->ai < rhs.ai);
    }        
}c[100010];
int lb(int m)
{
    return m & (-m);
}
void ud(int p, int q)
{
    while(p <= n) {
        b[p] += q;
        p += lb(p);
    }
}
int get(int x)
{
    int sum = 0;
    while(x > 0) {
        sum += b[x];
        x -= lb(x);
    }
    return sum;
}
int main()
{
    cin >> n;            
    for(int i = 1;i <= n;i++){
        cin >> c[i].aa;
		c[i].ai = i;    	
	}
    sort(c + 1, c + n + 1); 
    int ans = 0; 
    for(int i = 1;i <= n;i++) { 
//        cout << c[i].aa << " - " << c[i].ai << endl;
        ud(c[i].ai, 1);
        ans += c[i].ai - get(c[i].ai);
    }
    cout << ans << endl;
    return 0;
}