20250610 finished.

src/problem/mod.rs

@@ -702,3 +702,5 @@ mod p3170_lexicographically_minimum_string_after_removing_stars;
 mod p386_lexicographical_numbers;
 
 mod p440_k_th_smallest_in_lexicographical_order;
+
+mod p3442_maximum_difference_between_even_and_odd_frequency_i;

src/problem/p3442_maximum_difference_between_even_and_odd_frequency_i.rs

@@ -0,0 +1,44 @@
+/**
+ * [3442] Maximum Difference Between Even and Odd Frequency I
+ */
+pub struct Solution {}
+
+// submission codes start here
+use std::collections::HashMap;
+
+impl Solution {
+    pub fn max_difference(s: String) -> i32 {
+        let mut frequency_map = HashMap::new();
+
+        for c in s.bytes() {
+            let entry = frequency_map.entry(c).or_insert(0);
+            *entry += 1;
+        }
+
+        let mut odd_max = 0;
+        let mut even_min = i32::MAX;
+
+        for &v in frequency_map.values() {
+            if v % 2 == 0 {
+                even_min = even_min.min(v);
+            } else {
+                odd_max = odd_max.max(v);
+            }
+        }
+
+        odd_max - even_min
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_3442() {
+        assert_eq!(3, Solution::max_difference("aaaaabbc".to_string()));
+        assert_eq!(1, Solution::max_difference("abcabcab".to_string()));
+    }
+}