Submission #887086

#	Time	Username	Problem	Language	Result	Execution time	Memory
887086		phong	Palindromes (APIO14_palindrome)	C++17	47 / 100	1033 ms	100704 KiB

palindrome

#include<bits/stdc++.h>

#define ll long long
#define int long long

const int nmax = 3e5 + 5;
const ll oo = 1e18;
const int lg = 20;
const int base = 4000;
const ll mod = 1e9 + 7;
#define pii pair<int, int>
#define fi first
#define se second
#define int long long
#define debug(a, n) for(int i = 1; i <= n; ++i) cout << a[i] << ' ';
using namespace std;


int n, cur = 0;
string s;
int pw[nmax], h[nmax], rh[nmax];

void Init(){
    pw[0] = 1;
    for(int i = 1; i <= n; ++i){
        pw[i] = pw[i - 1] * base % mod;
        h[i] = (h[i - 1] * base + s[i] - 'a' + 1) % mod;
    }
    reverse(s.begin(), s.end());
    for(int i = 1; i <= n; ++i) rh[i] = (rh[i - 1] * base + s[i] - 'a' + 1) % mod;
    reverse(s.begin(), s.end());

}
int get(int l, int r, int h[]){
    return (h[r] - h[l - 1] * pw[r - l + 1] + mod * mod) % mod;
}

bool check(int l, int r){
    return get(l, r, h) == get(n - r + 1, n - l + 1, rh);
}
map<int, int> mp, f, par, ind;
int cnt[nmax];

void update(int l, int r){
    int u = l, v = r;
    bool ok = 1;
    while(l <= r){
        int x = get(l, r, h);
        if(++mp[x] == 1){
            ind[x] = ++cur;
            if(ok){
                f[cur]++;
                ok = 0;
            }
            cnt[cur] = r - l + 1;
            if(l + 1 <= r - 1){
                par[x] = get(l + 1, r - 1, h);
            }
        }
        else{
            if(ok){
                int id = ind[x];
                f[id]++;
            }
            break;
        }
        ++l, --r;
    }
}
vector<int> adj[nmax];
void dfs(int u){
    for(auto v : adj[u]){
        dfs(v);
        f[u] += f[v];
    }
}
main(){
    ios_base::sync_with_stdio(0);
//    cin.tie(0);cout.tie(0);
//    freopen("code.inp", "r", stdin);
//    freopen("code.out", "w", stdout);
    cin >> s;
    n = s.size(); s = ' ' + s + ' ';
    Init();
    for(int i = 1; i <= n; ++i){
        int l = 1, r = min(i, n - i + 1), kq = 1;
        while(l <= r){
            int mid = r + l >> 1;
            if(check(i - mid + 1, i + mid - 1)){
                kq = mid;
                l = mid + 1;
            }
            else r = mid - 1;
        }
        update(i - kq + 1, i + kq - 1);
        l = 1, r = min(i, n - i), kq = -1;
        while(l <= r){
            int mid = r + l >> 1;
            if(check(i - mid + 1, i + mid)){
                kq = mid;
                l = mid + 1;
            }
            else r = mid - 1;
        }
        if(kq != -1) update(i - kq + 1, i + kq);
    }
    for(auto [x, y] : mp){
        int v = ind[x];
        int u = ind[par[x]];
        adj[u].push_back(v);
    }
    dfs(0);
    ll ans = 0;
    for(int i = 1; i <= cur; ++i){
//        cout << f[i]
        ans = max(ans, f[i] * cnt[i]);
    }
    cout << ans;
}
/*

*/

Compilation message (stderr)

palindrome.cpp: In function 'void update(long long int, long long int)':
palindrome.cpp:45:9: warning: unused variable 'u' [-Wunused-variable]
   45 |     int u = l, v = r;
      |         ^
palindrome.cpp:45:16: warning: unused variable 'v' [-Wunused-variable]
   45 |     int u = l, v = r;
      |                ^
palindrome.cpp: At global scope:
palindrome.cpp:77:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   77 | main(){
      | ^~~~
palindrome.cpp: In function 'int main()':
palindrome.cpp:88:25: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   88 |             int mid = r + l >> 1;
      |                       ~~^~~
palindrome.cpp:98:25: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   98 |             int mid = r + l >> 1;
      |                       ~~^~~

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 0 / 26
• Subtask 5: 0 / 27