solved: 387. First Unique Character in a String

Signed-off-by: rajput-hemant <[email protected]>

Author: rajput-hemant

src/0301-0400/387 - First Unique Character in a String/first_unique_char_in_a_string.rs

@@ -0,0 +1,21 @@
+impl Solution {
+    pub fn first_uniq_char(s: String) -> i32 {
+        let mut map = std::collections::HashMap::new();
+        for c in s.chars() {
+            // increase the count of the character if exists
+            // otherwise insert the character w/ default value 0
+            // then increase the count by 1
+            *map.entry(c).or_insert(0) += 1;
+        }
+
+        // iterate over the string and return the index of the first character
+        // that has a count of 1
+        for (i, c) in s.chars().enumerate() {
+            if *map.get(&c).unwrap() == 1 {
+                return i as i32;
+            }
+        }
+
+        -1
+    }
+}