Update 字符串相关.md

blogs/Algorithm/剑指 Offer/字符串相关.md

@@ -24,3 +24,43 @@ class Solution {
 }
 ```
 
+[50. 第一个只出现一次的字符](https://leetcode-cn.com/problems/di-yi-ge-zhi-chu-xian-yi-ci-de-zi-fu-lcof/)
+
+```java
+class Solution {
+    public char firstUniqChar(String s) {
+        if (s.length() == 0) {
+            return ' ';
+        }
+        LinkedHashMap<Character, Integer> map = new LinkedHashMap<>();
+        for (char c : s.toCharArray()) {
+            map.put(c, map.getOrDefault(c, 0) + 1);
+        }
+        for (Map.Entry<Character, Integer> entry : map.entrySet()) {
+            if (entry.getValue() == 1) {
+                return entry.getKey();
+            }
+        }
+        return ' ';
+    }
+}
+```
+
+```java
+class Solution {
+    public char firstUniqChar(String s) {
+        char[] array = s.toCharArray();
+        int[] ints = new int[256];
+        for (char c : array) {
+            ints[c]++;
+        }
+        for (char c : array) {
+            if (ints[c] == 1) {
+                return c;
+            }
+        }
+        return ' ';
+    }
+}
+```
+