剑指offer-问题35

package offer;

import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;

/**
 * offer interview 35
 */
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();

        int idx = Integer.MAX_VALUE;
        char result = '\0';

        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"));
        System.out.println(firstNotRepeatingChar("aabccdbd")); // '\0'
        System.out.println(firstNotRepeatingChar("abcdefg")); // a
        System.out.println(firstNotRepeatingChar("gfedcba")); // g
        System.out.println(firstNotRepeatingChar("zgfedcba")); // z
    }
}

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