Added ransom note solution.

README.md

@@ -168,6 +168,7 @@ programming challenges completed in other languages.
 - [Find Smallest Letter Greater than Target](https://leetcode.com/problems/find-smallest-letter-greater-than-target)
 - [Count Negative Numbers](https://leetcode.com/problems/count-negative-numbers-in-a-sorted-matrix)
 - [Guess Number](https://leetcode.com/problems/guess-number-higher-or-lower/)
+- [Ransom Note](https://leetcode.com/problems/ransom-note)
 
 #### Medium
 
@@ -252,7 +253,7 @@ programming challenges completed in other languages.
 - [Minimum Size SubArray](https://leetcode.com/problems/minimum-size-subarray-sum)
 - [Rotate Image](https://leetcode.com/problems/rotate-image)
 - [Set Matrix Zeroes](https://leetcode.com/problems/set-matrix-zeroes)
- 
+
 #### Hard
 
 - [Kth Smallest Pair Distance](https://leetcode.com/problems/find-k-th-smallest-pair-distance)

src/leetcode/mod.rs

@@ -103,6 +103,7 @@ mod prime_set_bits;
 mod prime_subtraction;
 mod product_except_self;
 mod product_sum_digits;
+mod random_note;
 mod randomized_set;
 mod range_freq;
 mod range_sum_query;

src/leetcode/random_note.rs

@@ -0,0 +1,20 @@
+pub fn can_construct(ransom_note: String, magazine: String) -> bool {
+    let mut characters = [0i32; 26];
+    magazine.bytes().for_each(|b| {
+        characters[b as usize - 97] += 1;
+    });
+    ransom_note.bytes().for_each(|b| {
+        characters[b as usize - 97] -= 1;
+    });
+    characters.iter().all(|&x| x >= 0)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn determines_if_ransom_note_can_be_constructed_from_magazine() {
+        assert!(can_construct("aa".to_string(), "aab".to_string()))
+    }
+}