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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3. #define endl '\n'
  4. #define int long long
  5. const int MOD = pow(10,9)+7;
  6. const int MOD2 = 998244353;
  7. const int INF = LLONG_MAX/2;
  8.  
  9. int primes[1000000];
  10.  
  11. void seive(){
  12.     fill(primes, primes + 1000000, 1);
  13.     primes[0] = primes[1] = 0;
  14.     for(int i = 2 ; i*i < 1000000 ; i++){
  15.         if(primes[i]){
  16.             for(int j = i*i ; j < 1000000 ; j += i){
  17.                 primes[j] = 0;
  18.             }
  19.         }
  20.     }
  21. }
  22. int factorial(int n){
  23.     if(n==0){
  24.         return 1;
  25.     }
  26.     return (n*(factorial(n-1)))%MOD;
  27. }
  28. bool isPrime(int n){
  29.     if(n <= 1) return false;
  30.     for(int i = 2 ; i*i <= n ; i++){
  31.         if(n % i == 0) return false;
  32.     }
  33.     return true;
  34. }
  35.  
  36. int power(int a, int b){
  37.     if(b == 0) return 1;
  38.     a %= MOD;
  39.     int value = power(a, b / 2);
  40.     if(b % 2 == 0){
  41.         return (value * value) % MOD;
  42.     } else {
  43.         return ((value * value) % MOD * (a % MOD)) % MOD;
  44.     }
  45. }
  46.  
  47. int gcd(int a, int b){
  48.     if(a == 0) return b;
  49.     return gcd(b % a, a);
  50. }
  51. void dfs(int node , vector<int>A[] , int visited[] , int sum[] , int parent[] , int values[]){
  52.     visited[node] = 1;
  53.     for(auto node1 : A[node]){
  54.         if(!visited[node1]){
  55.             parent[node1] = node;
  56.             dfs(node1,A,visited,sum,parent,values);
  57.         }
  58.     }
  59.     int s = 0;
  60.     for(auto node1 : A[node]){
  61.         if(parent[node]!=node1){
  62.             s = max(s,sum[node1]);
  63.         }
  64.     }
  65.     sum[node] = values[node]+s;
  66. }
  67. int spf[1000001];
  68. void SPF(){
  69.    for(int i = 2 ; i<=1000000 ; i++){
  70.        spf[i] = i;
  71.    }
  72.    for(int i = 2 ; i<=sqrt(1000000) ; i++){
  73.         if(spf[i]==i){
  74.             for(int j = i*i ; j<=1000000 ; j+=i){
  75.                 if(spf[j]==j){
  76.                 spf[j] = i;
  77.                 }
  78.             }
  79.         }
  80.    }
  81. }
  82. void solve() {
  83.          int n;
  84.          cin>>n;
  85.          string words[n];
  86.          for(int i = 0 ; i<n; i++){
  87.             cin>>words[i];
  88.          }
  89.          map<string,int>mp;
  90.         for(int i = 0 ; i<n ; i++){
  91.             mp[words[i]]++;
  92.         }
  93.         int cnt = 0;
  94.         bool flag = false;
  95.         for(int i = 0 ; i<n ; i++){
  96.             if(words[i][0]!=words[i][1]){
  97.                 string r = words[i];
  98.                 reverse(r.begin(),r.end());
  99.                 if(mp[r]>0){
  100.                     cnt += (min(mp[words[i]],mp[r]))*4;
  101.                     mp.erase(words[i]);
  102.                     mp.erase(r);
  103.                 }
  104.             }
  105.             else if(words[i][0]==words[i][1]){
  106.                 int cnt1 = mp[words[i]];
  107.                 if(cnt1%2==0){
  108.                     cnt += (cnt1)*2;
  109.                 }
  110.                 else{
  111.                     if(!flag){
  112.                         cnt += (cnt1*2);
  113.                         flag = true;
  114.                     }
  115.                     else{
  116.                         cnt += (cnt1-1)*2;
  117.                     }
  118.                 }
  119.                 mp.erase(words[i]);
  120.             }
  121.         }
  122.         cout<<cnt<<endl;
  123. } 
  124. signed main(){
  125.     ios::sync_with_stdio(false); cin.tie(NULL);
  126.     SPF();
  127.     //int t;
  128.     //cin >> t;
  129.     //while(t--){
  130.         solve();
  131.     //}
  132.     return 0;
  133. }
Success #stdin #stdout 0.01s 12904KB
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https://ideone.com/tjzXXS
language:
C++14 (gcc 8.3)
created:
12 hours ago
visibility:
public

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