import java.util.LinkedHashMap;

import java.util.Map;

import java.util.Set;

/**

* Author: 王俊超

* Date: 2015-06-11

* Time: 16:46

* Declaration: All Rights Reserved !!!

*/

public class Test35 {

public static char firstNotRepeatingChar(String s) {

if (s == null || s.length() < 1) {

throw new IllegalArgumentException("Arg should not be null or empty");

}

Map<Character, Integer> map = new LinkedHashMap<>();

for (int i = 0; i < s.length(); i++) {

char c = s.charAt(i);

if (map.containsKey(c)) {

map.put(c, -2);

} else {

map.put(c, i);

}

}

Set<Map.Entry<Character, Integer>> entrySet = map.entrySet();

// 记录只出现一次的字符的索引

int idx = Integer.MAX_VALUE;

// 记录只出现一次的字符

char result = '\0';

// 找最小索引对应的字符

for (Map.Entry<Character, Integer> entry : entrySet) {

if (entry.getValue() >= 0 && entry.getValue() < idx) {

idx = entry.getValue();

result = entry.getKey();

}

}

return result;

}

public static void main(String[] args) {

System.out.println(firstNotRepeatingChar("google")); // l

System.out.println(firstNotRepeatingChar("aabccdbd")); // '\0'

System.out.println(firstNotRepeatingChar("abcdefg")); // a

System.out.println(firstNotRepeatingChar("gfedcba")); // g

System.out.println(firstNotRepeatingChar("zgfedcba")); // g

}

}