2124. Check if All A's Appears Before All B's: AC

Author: tan-wei

src/solution/mod.rs

@@ -1603,3 +1603,4 @@ mod s2119_a_number_after_a_double_reversal;
 mod s2120_execution_of_all_suffix_instructions_staying_in_a_grid;
 mod s2121_intervals_between_identical_elements;
 mod s2122_recover_the_original_array;
+mod s2124_check_if_all_as_appears_before_all_bs;

src/solution/s2124_check_if_all_as_appears_before_all_bs.rs

@@ -0,0 +1,81 @@
+/**
+ * [2124] Check if All A's Appears Before All B's
+ *
+ * Given a string s consisting of only the characters 'a' and 'b', return true if every 'a' appears before every 'b' in the string. Otherwise, return false.
+ *  
+ * Example 1:
+ *
+ * Input: s = "aaabbb"
+ * Output: true
+ * Explanation:
+ * The 'a's are at indices 0, 1, and 2, while the 'b's are at indices 3, 4, and 5.
+ * Hence, every 'a' appears before every 'b' and we return true.
+ *
+ * Example 2:
+ *
+ * Input: s = "abab"
+ * Output: false
+ * Explanation:
+ * There is an 'a' at index 2 and a 'b' at index 1.
+ * Hence, not every 'a' appears before every 'b' and we return false.
+ *
+ * Example 3:
+ *
+ * Input: s = "bbb"
+ * Output: true
+ * Explanation:
+ * There are no 'a's, hence, every 'a' appears before every 'b' and we return true.
+ *
+ *  
+ * Constraints:
+ *
+ * 	1 <= s.length <= 100
+ * 	s[i] is either 'a' or 'b'.
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/check-if-all-as-appears-before-all-bs/
+// discuss: https://leetcode.com/problems/check-if-all-as-appears-before-all-bs/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn check_string(s: String) -> bool {
+        !s.chars().skip_while(|&x| x == 'a').any(|x| x == 'a')
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_2124_example_1() {
+        let s = "aaabbb".to_string();
+
+        let result = true;
+
+        assert_eq!(Solution::check_string(s), result);
+    }
+
+    #[test]
+    fn test_2124_example_2() {
+        let s = "abab".to_string();
+
+        let result = false;
+
+        assert_eq!(Solution::check_string(s), result);
+    }
+
+    #[test]
+    fn test_2124_example_3() {
+        let s = "bbb".to_string();
+
+        let result = true;
+
+        assert_eq!(Solution::check_string(s), result);
+    }
+}