Submission #401092

#	Time	Username	Problem	Language	Result	Execution time	Memory
401092		Falcon	Monochrome Points (JOI20_monochrome)	C++17	100 / 100	212 ms	6988 KiB

monochrome

#include <bits/stdc++.h>

#ifdef DEBUG
#include "debug.hpp"
#endif

using namespace std;

#define all(c)              (c).begin(), (c).end()
#define rall(c)             (c).rbegin(), (c).rend()
#define traverse(c, it)     for(auto it = (c).begin(); it != (c).end(); ++it)
#define rep(i, N)           for(int i = 0; i < (N); ++i)
#define rrep(i, N)          for(int i = (N) - 1; i >= 0; --i)
#define rep1(i, N)          for(int i = 1; i <= (N); ++i)
#define rep2(i, s, e)       for(int i = (s); i <= (e); ++i)
#define rep3(i, s, e, d)    for(int i = (s); (d) >= 0 ? i <= (e) : i >= (e); i += (d))

#ifdef DEBUG
#define debug(x...)         { \
                            ++dbg::depth; \
                            string dbg_vals = dbg::to_string(x); \
                            --dbg::depth; \
                            dbg::fprint(__func__, __LINE__, #x, dbg_vals); \
                            }

#define light_debug(x)      { \
                            dbg::light = true; \
                            dbg::dout << __func__ << ":" << __LINE__; \
                            dbg::dout << "  " << #x << " = " << x << endl; \
                            dbg::light = false; \
                            }
#else
#define debug(x...)         42
#define light_debug(x)      42
#endif


using ll = long long;

template<typename T>
inline T& ckmin(T& a, T b) { return a = a > b ? b : a; }

template<typename T>
inline T& ckmax(T& a, T b) { return a = a < b ? b : a; }


int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    
    #ifdef DEBUG
    freopen("debug", "w", stderr);
    #endif

    int n; cin >> n;
    vector<int> w, b; w.reserve(n), b.reserve(n);
    vector<int> w_p(2 * n), b_p(2 * n);
    rep(i, n << 1) {
        char c; cin >> c; 
        if(c == 'W') w.push_back(i), w_p[i] = 1;
        else b.push_back(i), b_p[i] = 1;
    }

    partial_sum(all(w_p), w_p.begin());
    partial_sum(all(b_p), b_p.begin());

    auto w_between = [&](int s, int e) {
        int k = (w_p[(e - 1 + 2 * n) % (2 * n)] - w_p[s] + n) % n;
        return k;
    };

    auto b_between = [&](int s, int e) {
        int k = (b_p[(e - 1 + 2 * n) % (2 * n)] - b_p[s] + n) % n;
        return k;
    };

    long long ans{};
    auto calc = [&](int k) {
        k = ((k % n) + n) % n;
        static vector<long long> cache(n, -1);
        if(~cache[k]) return cache[k];
        long long c{};
        rep(i, n) {
            int j = (i + k) % n;
            c += min(w_between(w[i], b[j]), b_between(b[j], w[i]));
        }
        ckmax(ans, c);
        debug(k, c);
        return cache[k] = c;
    };

    auto check = [&](int i) {
        return calc(i) - calc(i - 1) > 0;
    };

    if(n <= 5) { // Edge cases.
        rep(i, n) calc(i);
        cout << ans << '\n';
        return 0;
    }

    int t{-1};
    if(check(0)) {
        if(check(n - 1)) {
            int p{n >> 1};
            while(check(p)) ++p;
            p %= n;
            t = 0;
            for(int k{1 << __lg(p)}; k > 0; k >>= 1)
                if(t + k < p && check(t + k))
                    t += k;
        } else {
            t = 0;
            for(int k{1 << __lg(n)}; k > 0; k >>= 1)
                if(t + k < n && check(t + k))
                    t += k;
        }
    } else {
        if(check(n - 1))
            t = n - 1;
        else {
            int p{n >> 1};
            while(!check(p)) ++p;
            p %= n;
            t = p;
            for(int k{1 << __lg(n - p)}; k > 0; k >>= 1)
                if(t + k < n && check(t + k))
                    t += k;
        }
            
    }

    debug(t);
    assert(check(t) && !check(t + 1));

    cout << ans << '\n';

    #ifdef DEBUG
    dbg::dout << "\nExecution time: " << clock() * 1000 / CLOCKS_PER_SEC  << "ms" << endl;
    #endif

    return 0;
}

Compilation message (stderr)

monochrome.cpp: In lambda function:
monochrome.cpp:33:29: warning: statement has no effect [-Wunused-value]
   33 | #define debug(x...)         42
      |                             ^~
monochrome.cpp:88:9: note: in expansion of macro 'debug'
   88 |         debug(k, c);
      |         ^~~~~
monochrome.cpp: In function 'int main()':
monochrome.cpp:33:29: warning: statement has no effect [-Wunused-value]
   33 | #define debug(x...)         42
      |                             ^~
monochrome.cpp:133:5: note: in expansion of macro 'debug'
  133 |     debug(t);
      |     ^~~~~

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