NOJ [1148] Creating Palindrome

• 问题描述
• XadillaX likes to play with strings very much.
  His favorite string is palindrome. Once he come across with a string, XadillaX always wants to change it to a palindrome by resorting the letters.
  
  Now give you a string, you should tell him whether the string can be changed to a palindrome. If yes, you should output it. (The smallest one in Lexicographic order)
  

  
  
• 输入
• This problem contains several cases.
  Each case is a string, no longer than 20000. Only contains uppercase letters.
  
• 输出
• For each case, if it can be changed to a palindrome, output it. If can't, output 0.
  
  
  
  
  本题有点水。。。就不解释了
  
  

  #include<stdio.h>
  #include<string.h>
  
  int str[100];
  char letter[20010];
  char palindrome[20010];
  int main()
  {
    while(~scanf("%s",letter))
    {
      int i,j,len=strlen(letter);
      memset(str,0,sizeof(str));
      for (i = 0; i < len; ++i)
        str[letter[i]]++;
      int odd=0;
      for(i=65;i<=90;i++)
      {
        if(str[i]%2)
          odd++;
        if(odd>=2)
          break;
      }
      if(odd>=2)
        printf("0\n");
      else
      {
       int s=0,t=len-1;
        for(i=65;i<=90;i++)
        {
          if(str[i]%2==0 && str[i])//偶数个 且不为0 
          {
            while(str[i])
            {
              palindrome[s]=(char)i;
              s++;
              palindrome[t]=(char)i;
              t--;
              str[i]-=2;
            }
          }
          else if(str[i]%2)
          {
            palindrome[len/2]=(char)i;
            for(j=0;j<str[i]-1;j+=2)
            {
              palindrome[s]=(char)i;
              s++;
              palindrome[t]=(char)i;
              t--;
            }
          }
        }
    palindrome[len]='\0';
        printf("%s\n",palindrome );
      }
    }
    return 0;
  }