https://www.acmicpc.net/problem/4442
#pragma GCC optimize ("O3")
#include <bits/stdc++.h>
#define fastio ios::sync_with_stdio(0), cin.tie(0), cout.tie(0)
#define int int64_t
using namespace std;
using pii = pair<int, int>;
template<typename T = int64_t, size_t sz = 17, typename F = plus<T>>
struct SegTree {
vector<T> tree; T t; F f{};
SegTree(T t = T()) : tree(1 << sz + 1, t), t(t) {}
explicit SegTree(T t, const F& f) : tree(1 << sz + 1, t), t(t), f(f) {}
void Init() {
for (int i = (1 << sz) - 1; i; i--) {
tree[i] = f(tree[i << 1], tree[i << 1 | 1]);
}
}
void Update(int i, T val) {
--i |= 1 << sz; tree[i] = val;
while (i >>= 1) tree[i] = f(tree[i << 1], tree[i << 1 | 1]);
}
T Query(int l, int r) {
T L = t, R = t; --l |= 1 << sz, --r |= 1 << sz;
while (l <= r) {
if (l & 1) L = f(L, tree[l++]);
if (~r & 1) R = f(tree[r--], R);
l >>= 1, r >>= 1;
}
return f(L, R);
}
};
int32_t main() {
fastio;
int n;
while(cin >> n && n != 0){
int r = 0;
SegTree<int,20> ST;
map<string,int> M;
for(int i = 0; i < n; i++){
string t; cin >> t;
M[t] = i + 1;
}
for(int i = 0; i < n; i++){
string s; cin >> s;
r += (M[s] - 1 - ST.Query(1, M[s]));
ST.Update(M[s], 1);
}
cout << r << "\n";
}
}
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
#define fastio ios::sync_with_stdio(0), cin.tie(0), cout.tie(0)
#define int int64_t
using namespace std;
using pii = pair<int, int>;
template <size_t sz>
struct FenwickTree
{
vector<int> tree;
FenwickTree() : tree(sz + 1) {}
void update(int i, int val)
{
for (; i <= sz; i += i & -i)
tree[i] += val;
}
int query(int i)
{
int ret = 0;
for (; i; i -= i & -i)
ret += tree[i];
return ret;
}
};
int32_t main(){
int n;
while(cin >> n && n != 0){
int r = 0;
FenwickTree<100001> FT;
map<string,int> M;
vector<pii> v(n);
for(int i = 0; i < n; i++){
string s; cin >> s;
M[s] = i + 1;
}
for(int i = 0; i < n; i++){
string s; cin >> s;
int idx = M[s];
v[i] = {idx, i + 1};
}
sort(v.begin(), v.end());
for(int i = n - 1; i >= 0; i--){
int t = v[i].second;
r += FT.query(t - 1);
FT.update(t, 1);
}
cout << r << "\n";
}
}
입력이 문자열로 들어오기 때문에 map을 사용해서 판별을 해주어야합니다.
FenwickTree를 사용해서 뒤에서부터 inversion의 값을 판별해주면 됩니다.