提出 #23594972

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ソースコード 拡げる

/* 
As soon as man understands that it is only the Qualities which act
        and nothing else, and perceives that which is beyond,
            he attains My divine nature.

When the soul transcends the Qualities,
         which are the real cause of physical existence,
            then, freed from birth and death,
                 from old age and misery, he quaffs the nectar of
                                Immortality.
                                                  -- "SHRI BHAGVAT GITA"
 -----------------------------------------------------------------------
 */
#include <bits/stdc++.h>
using namespace std; 
typedef long long int ll;
#define pb push_back 
#define popb pop_back
#define mp make_pair
#define ve vector
#define vii vector < int >
#define vll vector < ll > 
#define pii pair < int , int >
#define pll pair < ll , ll >
#define vpl vector < pll >
#define fi first
#define sz size 
#define len length 
#define se second 
//const ll mod=998244353;
const ll mod = 1000000000+7;
const ll N=10000000+6;
const ll INFF=1000000000000000000;
#define M_PI           3.14159265358979323846
//--------------------------------------------

//------------------------------------
vii parent(300000);
vii sized(300000);

void make()
{   
    for(int i = 0; i <= 299999; i++)
        parent[i] = i , sized[i] = 1;

}

//-------------------------------------------
int find(int  a)
{
    if(a == parent[a]) return a;
    return parent[a] = find(parent[a]);
}

void merge(int  a , int b)
{
    a = find(a) ; b = find(b);
    if(a != b)
    {
        parent[b] = a;
        sized[a] += sized[b];
    }
}



//============================================
int main() {
    ios::sync_with_stdio(false);
     cin.tie(0);
     cout.tie(0);
    #ifndef ONLINE_JUDGE
       freopen ("INPUT.txt" , "r" , stdin);
       freopen ("OUTPUT.txt", "w" , stdout);
    #endif

        int n;
        cin >> n;

        make();
        int arr[n];
        for(int i = 0; i < n; i++) cin >> arr[i];

        int l = 0 , r = n-1;

        while(l < r){
            if(arr[l] == arr[r]) {
                l++;r--;
            }
            else
            {
                merge(arr[l] , arr[r]);
                l++, r--;
            }
        }
        ll ans = 0;
        vii vis(250030);
        for(int i = 1; i <= 250000; i++)
            {
                int g = find(i);
                if(!vis[g])
                {
                    vis[g] = 1;
                    ans = ans + sized[g] - 1;
                }
            }

            cout << ans;




       


return 0;
} 

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