Submission #614053

#	Time	Username	Problem	Language	Result	Execution time	Memory
614053		MohamedAliSaidane	Monochrome Points (JOI20_monochrome)	C++14	100 / 100	982 ms	10680 KiB

monochrome

#include<bits/stdc++.h>

    using namespace std;

    typedef long long ll;

    typedef pair<int,int> pii;
    typedef pair<ll,ll> pll;

    typedef vector<int> vi;
    typedef vector<ll> vll;
    typedef vector<pii> vpi;
    typedef vector<pll> vpl;

    #define pb push_back
    #define popb pop_back
    #define all(x) (x).begin(), (x).end()


    #define ff first
    #define ss second

    const int nax = 4e5 + 4;
    int n;
    int col[nax];
    ll dp[nax];
    vi perm, ot;

    struct FenwickTree
    {
        vector<int> bit;  // binary indexed tree
        int n;

        FenwickTree(int n) {
            this->n = n;
            bit.assign(n, 0);
        }

        FenwickTree(vector<int> a) : FenwickTree(a.size()) {
            for (size_t i = 0; i < a.size(); i++)
                add(i, a[i]);
        }

        int sum(int r) {
            int ret = 0;
            for (; r >= 0; r = (r & (r + 1)) - 1)
                ret += bit[r];
            return ret;
        }

        int sum(int l, int r) {
            return sum(r) - sum(l - 1);
        }

        void add(int idx, int delta) {
            for (; idx < n; idx = idx | (idx + 1))
                bit[idx] += delta;
        }
    };

    ll compute(int x)
    {
        if(x >= n)
            return 0 ;
        if(dp[x] != -1)
            return dp[x];
        vpi inter;
        ll rep = 0;
        for(int i=  0 ; i < n; i++)
        {
            int a = perm[(i + x)%n];
            int b = ot[i];
            inter.pb({min(a,b), max(a,b)});
        }
        sort(all(inter));
        reverse(all(inter));
        FenwickTree fen = FenwickTree(2 * n);
        for(int i=  0 ; i < n; i++)
        {
            int a = inter[i].ff;
            int b=  inter[i].ss;
            rep += (ll)(fen.sum(a,b));
            fen.add(a, 1);
            fen.add(b, -1);
        }
        return dp[x] = rep;

    }
    int32_t main()
    {
        ios::sync_with_stdio(false);
        cin.tie(0); cout.tie(0);
        memset(dp, -1,sizeof(dp));
        cin >> n;
        for(int i  = 0 ; i < 2 * n ; i++)
        {
            char c; cin >> c;
            if(c == 'B')
                col[i] = 1;
            if(col[i])
                perm.pb(i);
            else
                ot.pb(i);
        }
        ll ans = 0 ;
        int debut = 0;
        int fin = n - 1;
        int rep = debut;
        while(debut <= fin )
        {
            int mid = (debut + fin)/2;
            //cout << mid << ' ' << compute(mid) << ' ' << compute(mid + 1) << "\n";
            if(compute(mid + 1) > compute(mid))
            {
                rep = mid + 1;
                debut = mid + 1;
                ans = max(ans, compute(mid + 1));
            }
            else
            {
                rep = mid ;
                fin = mid - 1;
                ans = max(ans, compute(mid ));
            }
        }
        cout << ans;
    }

Compilation message (stderr)

monochrome.cpp: In function 'int32_t main()':
monochrome.cpp:108:13: warning: variable 'rep' set but not used [-Wunused-but-set-variable]
  108 |         int rep = debut;
      |             ^~~

• Subtask 1: 4 / 4
• Subtask 2: 21 / 21
• Subtask 3: 10 / 10
• Subtask 4: 65 / 65