Submission #855998

#	Time	Username	Problem	Language	Result	Execution time	Memory
855998		RiverFlow	Love Polygon (BOI18_polygon)	C++14	21 / 100	133 ms	88840 KiB

polygon

#include <bits/stdc++.h>

#define nl "\n"
#define no "NO"
#define yes "YES"
#define fi first
#define se second
#define vec vector
#define task "main"
#define _mp make_pair
#define ii pair<int, int>
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define evoid(val) return void(std::cout << val)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FOD(i, b, a) for(int i = (b); i >= (a); --i)
#define unq(x) sort(all(x)); x.resize(unique(all(x)) - x.begin())

using namespace std;

template<typename U, typename V> bool maxi(U &a, V b) {
    if (a < b) { a = b; return 1; } return 0;
}
template<typename U, typename V> bool mini(U &a, V b) {
    if (a > b or a == -1) { a = b; return 1; } return 0;
}

const int N = (int)2e5 + 9;
const int mod = (int)1e9 + 7;

void prepare(); void main_code();

int main() {
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if (fopen(task".inp", "r")) {
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }
    const bool MULTITEST = 0; prepare();
    int num_test = 1; if (MULTITEST) cin >> num_test;
    while (num_test--) { main_code(); }
}

void prepare() {};

int n, g[N];

int dp[21][1 << 20];

void subtask1() {
    memset(dp, -1, sizeof dp); dp[0][0] = 0;
    FOR(i, 0, n - 1)
    FOR(mask, 0, (1 << n) - 1) if (dp[i][mask] != -1) {
        if (1 & (mask >> i)) {
            mini(dp[i + 1][mask], dp[i][mask]);
            continue ;
        }
        FOR(k, 0, n - 1) if ( k != i and (1 & (mask >> k)) == 0 ) {
            mini(dp[i + 1][mask | (1 << k) | (1 << i)],
                 dp[i][mask] + (g[i + 1] != k + 1)
                             + (g[k + 1] != i + 1));
        }
    }
    cout << dp[n][ (1 << n) - 1 ];
}

int deg[N], vis[N];

void main_code() {
    cin >> n; map<string, int> mp;
    for(int i = 1, cnt = 0; i <= n; ++i) {
        string x, y; cin >> x >> y;
        if (mp.find(x) == mp.end()) {
            mp[x] = ++cnt;
        }
        if (mp.find(y) == mp.end()) {
            mp[y] = ++cnt;
        }
        int a = mp[x], b = mp[y];
        g[a] = b;
    }
    if (n <= 20)
        return subtask1(), void();
    FOR(i, 1, n) ++deg[g[i]];
    bool sub2 = 1;
    FOR(i, 1, n) sub2 &= (deg[i] == 1);
    if (sub2) {
        int res = 0;
        FOR(i, 1, n) if (vis[i] == 0) {
            int cnt = 1; vis[i] = 1;
            for(int j = g[i]; j != i; j = g[j]) {
                ++cnt; vis[j] = 1;
            }
            res += (cnt + 1) / 2;
        }
        cout << res;
        return ;
    }
}


/*     Let the river flows naturally     */

Compilation message (stderr)

polygon.cpp: In function 'int main()':
polygon.cpp:36:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   36 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
polygon.cpp:37:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   37 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 21 / 21
• Subtask 2: 0 / 25
• Subtask 3: 0 / 29
• Subtask 4: 0 / 25