#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/rope>
using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_cxx;
typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;
typedef pair<int, int> pi;
typedef pair<ll,ll> pl;
typedef pair<ld,ld> pd;
typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;
template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;
#define FOR(i, a, b) for (int i=a; i<(b); i++)
#define F0R(i, a) for (int i=0; i<(a); i++)
#define FORd(i,a,b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i,a) for (int i = (a)-1; i >= 0; i--)
#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
const int MOD = 1000000007;
const ll INF = 1e18;
const int MX = 100001;
int n;
vi s;
void compress() {
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n; s.resize(n);
map<int,int> m;
F0R(i,n) {
cin >> s[i];
m[s[i]] = 0;
}
int co = 0;
for (auto& a: m) a.s = co++;
for (int& i: s) i = n-1-m[i];
}
int notInv(vi st) {
int ret = 0;
F0R(i,sz(st)) FOR(j,i+1,sz(st)) if (st[i] < st[j]) ret ++;
return ret;
}
int comb(int x) { return x*(x-1)/2; }
pair<int,vpi> test(vi z) {
vpi S; F0R(i,sz(s)) S.pb({s[i],1});
int lst = -1, notFixed = 0, getFixed = 0;
vi st;
int c = 0;
vi zz;
F0R(i,n) {
if (find(all(z),S[i].f) != z.end()) {
st.pb(S[i].f);
S[i].s = 0;
notFixed ++;
getFixed += c;
} else {
if (S[i].f < lst) return {MOD,{}};
lst = S[i].f;
c ++;
zz.pb(S[i].f);
}
}
for (int i: st) for (int j: zz) if (i > j) getFixed ++;
// cout << notInv(st)+comb(notFixed)+2*notFixed+getFixed << "\n";
vpi v;
int cur = 0;
F0Rd(i,n) {
int ind = 0; while (S[ind].f != i) ind ++;
if (S[ind].s) continue;
cur += ind+1; S.erase(S.begin()+ind);
int lst = 0;
F0R(j,n-1) if (S[j].s && S[j].f < i) lst = j+1;
cur += lst+1; S.insert(S.begin()+lst,{i,1});
v.pb({ind+1,lst+1});
}
return {cur,v};
}
pi dp[1001][1001];
int pos[1001];
void MN(pi& a, pi b) { a = min(a,b); }
int main() {
compress();
s.pb(n);
F0R(i,sz(s)) pos[s[i]] = i;
F0R(i,n+1) F0R(j,n+1) dp[i][j] = {MOD,MOD};
dp[n][n] = {0,MOD};
F0Rd(i,n) {
int a = 1; F0R(j,pos[i]) if (s[j] < i) a ++;
a ++;
F0R(j,n+1) {
if (s[j] < i) a ++;
MN(dp[i][j],{dp[i+1][j].f+a,j});
}
int c = 0;
FOR(k,pos[i]+1,n+1) {
MN(dp[i][pos[i]],{dp[i+1][k].f+c,k});
c += max(i-s[k],0);
}
}
int bes = 0;
F0R(i,n+1) if (dp[0][i].f < dp[0][bes].f) bes = i;
pi cur = {0,bes};
vi move;
while (cur.f < n) {
// cout << "OOPS " << cur.f << " " << cur.s << "\n";
if (dp[cur.f][cur.s].s == cur.s) move.pb(cur.f);
cur = {cur.f+1,dp[cur.f][cur.s].s};
}
/*for (int i: move) cout << i << " ";
cout << "\n";*/
auto a = test(move);
cout << sz(a.s) << "\n";
for (auto x: a.s) {
cout << x.f << " " << x.s << "\n";
}
}
/* Look for:
* the exact constraints (multiple sets are too slow for n=10^6 :( )
* special cases (n=1?)
* overflow (ll vs int?)
* array bounds
* if you have no idea just guess the appropriate well-known algo instead of doing nothing :/
*/
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
376 KB |
Output is correct |
| 2 |
Correct |
2 ms |
484 KB |
Output is correct |
| 3 |
Correct |
3 ms |
548 KB |
Output is correct |
| 4 |
Correct |
2 ms |
692 KB |
Output is correct |
| 5 |
Correct |
3 ms |
852 KB |
Output is correct |
| 6 |
Correct |
3 ms |
1620 KB |
Output is correct |
| 7 |
Correct |
7 ms |
4512 KB |
Output is correct |
| 8 |
Correct |
13 ms |
6816 KB |
Output is correct |
| 9 |
Correct |
16 ms |
8452 KB |
Output is correct |
| 10 |
Correct |
17 ms |
8496 KB |
Output is correct |
