gistfile1.java

class Solution{
  /*
  * Time complexity O(n); Space complexity O(1).
  */
  public boolean isAllUniqChar(String str){
    if(str == null) return false; // Make sure that the string is valid.
    
    boolean[] temp = new boolean[128]; // Temp stores all 128 ASCII characters' presences in the string.
    char[] chars = str.toCharArray(); // Convert the string into Char array so that we can iterate each character.
    
    for(boolean i in:temp) i = false; // Initialize the temp array.
    
    for(char c in:chars){
      int index = c; // Get the ASCII value of a char.
      if(!temp[index]) temp[index] = true; // Check if this char has showed up before. If not, mark its presence then proceed.
      else return false; // If this char has showed up once, then this string has duplicate chars.
    }
    
    return true; // All chars are unique.
  }
}

Can I comment this?

额。。

cool