题解 | #找出字符串中第一个只出现一次的字符#

import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.HashMap; import java.util.HashSet; import java.util.Map; import java.util.Set;

public class Main { public static void main(String[] args) throws IOException { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String s = ""; while ((s = br.readLine()) != null) { Map<Character, Integer> map = new HashMap<>(); for (char c: s.toCharArray()) { map.put(c, map.getOrDefault(c, 0).intValue() + 1); } Set set = new HashSet<>(); for (Map.Entry<Character, Integer> entry: map.entrySet()) { if (entry.getValue().intValue() == 1) { set.add(entry.getKey()); } } if (set.size() == 0) { System.out.println(-1); } else { for (char c : s.toCharArray()) { if (set.contains(c)) { System.out.println(c); break; } } } } br.close(); } }