D2.cpp

// #pragma GCC optimize("Ofast,unroll-loops")
// #pragma GCC target("avx,avx2,fma")

#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define ull unsigned long long
#define dd double
#define ld long double
#define sl(n) scanf("%lld", &n)
#define si(n) scanf("%d", &n)
#define sd(n) scanf("%lf", &n)
#define pll pair <ll, ll>
#define pii pair <int, int>
#define mp make_pair
#define pb push_back
#define all(v) v.begin(), v.end()
#define inf (1LL << 61)
#define loop(i, start, stop, inc) for(ll i = start; i <= stop; i += inc)
#define for1(i, stop) for(ll i = 1; i <= stop; ++i)
#define for0(i, stop) for(ll i = 0; i < stop; ++i)
#define rep1(i, start) for(ll i = start; i >= 1; --i)
#define rep0(i, start) for(ll i = (start-1); i >= 0; --i)
#define ms(n, i) memset(n, i, sizeof(n))
#define casep(n) printf("Case %lld:", ++n)
#define pn printf("\n")
#define pf printf
#define EL '\n'
#define fastio std::ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);

const ll sz = 1e5 + 10;
vector <int> pos[sz];
ll dp[sz], ara[sz], ara2[sz], idx;

ll solve(ll i)
{
    if(i > idx)
        return 0;

    ll &ret = dp[i];
    if(ret != -1)
        return ret;

    ret = 1+solve(i+1);

    if(i > 1) {
        ll val = ara2[i-1];
        ll nxt = upper_bound(all(pos[val]), i) - pos[val].begin();

        if(nxt < pos[val].size()) {
            ll np = pos[val][nxt];
            ll ad = (np-i-1);

            ret = min(ret, ad + solve(np));
        }

    }

    ll val = ara2[i];
    ll nxt = upper_bound(all(pos[val]), i) - pos[val].begin();

    if(nxt < pos[val].size()) {
        ll np = pos[val][nxt];
        ll ad = (np-i-1);

        ret = min(ret, ad+solve(np));
    }

    return ret;
}

int main()
{
    ll n;
    cin >> n;
    for1(i, n) sl(ara[i]);

    for1(i, n) {

        ll stop;
        for(ll j = i; j <= n; j++) {
            if(ara[i] != ara[j])
                break;

            stop = j;
        }

        ara2[++idx] = ara[i];
        pos[ ara[i] ].pb(idx);
        i = stop;
    }

    ms(dp, -1);
    cout << solve(1) << EL;

    return 0;
}