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209 · First Unique Character in a String - LintCode

# Description

Given a string and find the first unique character in a given string. You can assume that there is at least one unique character in the string.

# Example

Example 1:
	Input: "abaccdeff"
	Output:  'b'
	
	Explanation:
	There is only one 'b' and it is the first one.


Example 2:
	Input: "aabccd"
	Output:  'b'
	
	Explanation:
	'b' is the first one.

# Solution

Data stream 簡易寫法

public class Solution {
    /**
     * @param str: str: the given string
     * @return: char: the first unique character in a given string
     */
    public char firstUniqChar(String str) {
      List<Character> list = new ArrayList<>();
      boolean[] isRepeated = new boolean[256];
      
      for (int i = 0; i < str.length(); i++){
          char c = str.charAt(i);
          
          if (!isRepeated[c]) {
              if (list.contains(c)) {
                  list.remove((Character)c);
//remove (Object o) ，不強改成 (character) 會 IndexOutOfBoundsException:  
// 因為 java 會把它轉成 ASCII, a-> 97
// 本來 arraylist remove (index);
// 它會以為你 remove 的是在 鏈表裡 index=97 的數
				isRepeated[c] = true;
              } else {
                  list.add(c);
              }
          }
      }
      return list.get(0);
    }
}