description: A string is called square if it is some string written twice in a row. For example, the strings "aa", "abcabc", "abab" and "baabaa" are square. But the strings "aaa", "abaaab" and "abcdabc" are not square.
  
  For a given string s determine if it is square.
  
  Input
  
  The first line of input data contains an integer t (1 ≤ t ≤ 100) —the number of test cases.
  
  This is followed by t lines, each containing a description of one test case. The given strings consist only of lowercase Latin letters and have lengths between 1 and 100 inclusive.
  
  Output
  
  For each test case, output on a separate line:
  
    * YES if the string in the corresponding test case is square, 
    * NO otherwise. 
  
  
  
  You can output YES and NO in any case (for example, strings yEs, yes, Yes and YES will be recognized as a positive response).
  
  Example
  
  Input
  
  
  10
  a
  aa
  aaa
  aaaa
  abab
  abcabc
  abacaba
  xxyy
  xyyx
  xyxy
  
  
  Output
  
  
  NO
  YES
  NO
  YES
  YES
  YES
  NO
  NO
  NO
  YES
solution: #include <bits/stdc++.h>
  int main(void) {
    int t, len, i, flag;
    char c[102];
    scanf("%d", &t);
    while (t--) {
      flag = 0;
      scanf("%s", c);
      len = strlen(c);
      if (len % 2 == 0) {
        flag = 1;
        for (i = 0; i < (len / 2) && flag; i++)
          if (c[i] != c[i + len / 2]) flag = 0;
      }
      if (flag)
        printf("YES\n");
      else
        printf("NO\n");
    }
    return 0;
  }
  