first-unique-character-in-a-strin

Author: bestgopher

README.md

@@ -6,6 +6,9 @@ leetcode by rust
 - 229：求众数 II
   - [src](https://leetcode-cn.com/problems/majority-element-ii/)
   - [leetcode](https://leetcode-cn.com/problems/majority-element-ii/)
+- 387：字符串中的第一个唯一字符
+  - [src](https://leetcode-cn.com/problems/first-unique-character-in-a-string/)
+  - [leetcode](https://leetcode-cn.com/problems/first-unique-character-in-a-string/)
 
 -  746：使用最小花费爬楼梯
 	- [src](https://github.com/rustors/leetcode/blob/main/src/bin/check-if-n-and-its-double-exist.rs) 

src/bin/first-unique-character-in-a-string.rs

@@ -0,0 +1,25 @@
+fn main() {}
+
+struct Solution;
+
+impl Solution {
+    /// 因为都是小写字母，所以最多只有26种字符，
+    /// 申请一个26位长的数组，循环遍历字符串，每个字符的下标对应位字符-'a'，
+    /// 每次循环，数组中对应下标的值+1；遍历字符串后，再遍历字符串一次，
+    /// 找到字符对应下标的值，值为1则说明只存在一次。因此对应的下标则为所求。
+    pub fn first_uniq_char(s: String) -> i32 {
+        let mut a = [0; 26];
+        let a_char = 'a' as usize;
+
+        for &i in s.as_bytes().iter() {
+            a[(i as usize) - a_char] += 1;
+        }
+
+        for (i, &value) in s.as_bytes().iter().enumerate() {
+            if a[(value as usize) - a_char] == 1 {
+                return i as i32;
+            }
+        }
+        -1
+    }
+}