SPOJ/EPALIN - 4103. Extend to Palindrome/epalin.2.cpp

   1 // Andrés Mejía
   2 using namespace std;
   3 #include <algorithm>
   4 #include <iostream>
   5 #include <iterator>
   6 #include <numeric>
   7 #include <sstream>
   8 #include <fstream>
   9 #include <cassert>
  10 #include <climits>
  11 #include <cstdlib>
  12 #include <cstring>
  13 #include <string>
  14 #include <cstdio>
  15 #include <vector>
  16 #include <cmath>
  17 #include <queue>
  18 #include <deque>
  19 #include <stack>
  20 #include <list>
  21 #include <map>
  22 #include <set>
  23
  24 #define foreach(x, v) for (typeof (v).begin() x=(v).begin(); x !=(v).end(); ++x)
  25 #define For(i, a, b) for (int i=(a); i<(b); ++i)
  26 #define D(x) cout << #x " is " << x << endl
  27
  28 const double EPS = 1e-9;
  29 int cmp(double x, double y = 0, double tol = EPS) {
  30     return (x <= y + tol) ? (x + tol < y) ? -1 : 0 : 1;
  31 }
  32
  33 const int MAXN = 100005 * 2;
  34
  35 int p[MAXN];
  36
  37 int main(){
  38     string s;
  39     s.reserve(MAXN);
  40     while (getline(cin, s)) {
  41         printf("%s", s.c_str());
  42         int n = s.size();
  43         s = s + "$" + s;
  44         reverse(s.begin(), s.begin() + n);
  45
  46         p[0] = 0;
  47         for (int i = 1; i < 2 * n + 1; ++i) {
  48             p[i] = p[i - 1];
  49             while (p[i] > 0 and s[i] != s[p[i]]) p[i] = p[p[i] - 1];
  50             if (s[i] == s[p[i]]) p[i]++;
  51         }
  52
  53         for (int i = p[2 * n]; i < n; ++i) {
  54             putchar(s[i]);
  55         }
  56         puts("");
  57     }
  58     return 0;
  59 }