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  1. #include <bits/stdc++.h>
  2.  
  3. #define debug     cout << "ok\n";
  4. #define SQR(x)    (1LL * ((x) * (x)))
  5. #define MASK(i)   (1LL << (i))
  6. #define BIT(x, i) (((x) >> (i)) & 1)
  7. #define fi        first
  8. #define se        second
  9. #define pb        push_back
  10.  
  11. #define mp make_pair
  12. #define pii pair<int,int>
  13. #define pli pair<ll,int>
  14. #define vi vector<int>
  15.  
  16. #define FAST ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
  17.  
  18. typedef long long ll;
  19. typedef unsigned long long ull;
  20. typedef long double ld;
  21. typedef unsigned int ui;
  22.  
  23. using namespace std;
  24.  
  25. const int M = 1e9 + 7;
  26. const int INF = 1e9 + 7;
  27. const ll INFLL = (ll)2e18 + 7LL;
  28. const ld PI = acos(-1);
  29.  
  30. const int dx[] = {1, -1, 0, 0, -1, 1, 1, -1};
  31. const int dy[] = {0, 0, 1, -1, -1, -1, 1, 1};
  32.  
  33. template<class _, class __>
  34.     bool minimize(_ &x, const __ y){
  35.         if(x > y){
  36.             x = y;
  37.             return true;
  38.         } else return false;
  39.     }
  40. template<class _, class __>
  41.     bool maximize(_ &x, const __ y){
  42.         if(x < y){
  43.             x = y;
  44.             return true;
  45.         } else return false;
  46.     }
  47.  
  48. template<class _,class __>
  49.     void Add(_ &x, const __ y) {
  50.         x += y;
  51.         if (x >= M) {
  52.             x -= M;
  53.         }
  54.         return;
  55.     }
  56.  
  57. template<class _,class __>
  58.     void Diff(_ &x, const __ y) {
  59.         x -= y;
  60.         if (x < 0) {
  61.             x += M;
  62.         }
  63.         return;
  64.     }
  65.  
  66. //--------------------------------------------------------------
  67.  
  68. const int MaxN = 1e6+7;
  69.  
  70. int n,cnt[26],f[MaxN][26][2],g[26][26],bf[26],a[MaxN];
  71.  
  72. void sol() {
  73.     cin >> n;
  74.     for (int i=1;i<=n;i++) {
  75.         char x;
  76.         cin >> x;
  77.         a[i] = x - 'a';
  78.     }
  79.     int res = 0;
  80.     memset(cnt,0,sizeof(cnt));
  81.     for (int i=1;i<=n;i++) {
  82.         cnt[a[i]]++;
  83.         bf[a[i]] = i;
  84.         for (int j=0;j<26;j++) {
  85.             if (bf[j]) {
  86.                 maximize(res,cnt[a[i]] - cnt[j] - f[bf[j]][a[i]][1]);
  87.                 maximize(res,cnt[j] - cnt[a[i]] - f[bf[j]][a[i]][0]);
  88.             }
  89.         }
  90.  
  91.         for (int j=0;j<26;j++) {
  92.             minimize(g[a[i]][j],(cnt[a[i]] - 1) - (cnt[j] - (a[i] == j)));
  93.             minimize(g[j][a[i]],(cnt[j] - (a[i] == j)) - (cnt[a[i]]-1));
  94.             f[i][j][0] = g[a[i]][j];
  95.             f[i][j][1] = g[j][a[i]];
  96.         }
  97.     }
  98.     cout << res;
  99. }
  100.  
  101. int main() {
  102. //	freopen("test.inp","r",stdin);
  103. //	freopen("test.out","w",stdout);
  104. 	FAST
  105. 	int t=1;
  106. // 	cout << sizeof(f) << '\n';
  107. //	cin >> t;
  108. 	while (t--) sol();
  109. }
  110.  
Success #stdin #stdout 0.01s 5320KB
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https://ideone.com/meVt5W
language:
C++14 (gcc 8.3)
created:
2 days ago
visibility:
public

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