1946. Largest Number After Mutating Substring: AC

Author: tan-wei

Diff for: src/solution/mod.rs

@@ -1467,3 +1467,4 @@ mod s1942_the_number_of_the_smallest_unoccupied_chair;
 mod s1943_describe_the_painting;
 mod s1944_number_of_visible_people_in_a_queue;
 mod s1945_sum_of_digits_of_string_after_convert;
+mod s1946_largest_number_after_mutating_substring;

Diff for: src/solution/s1946_largest_number_after_mutating_substring.rs

@@ -0,0 +1,104 @@
+/**
+ * [1946] Largest Number After Mutating Substring
+ *
+ * You are given a string num, which represents a large integer. You are also given a 0-indexed integer array change of length 10 that maps each digit 0-9 to another digit. More formally, digit d maps to digit change[d].
+ * You may choose to mutate a single substring of num. To mutate a substring, replace each digit num[i] with the digit it maps to in change (i.e. replace num[i] with change[num[i]]).
+ * Return a string representing the largest possible integer after mutating (or choosing not to) a single substring of num.
+ * A substring is a contiguous sequence of characters within the string.
+ *  
+ * Example 1:
+ *
+ * Input: num = "<u>1</u>32", change = [9,8,5,0,3,6,4,2,6,8]
+ * Output: "<u>8</u>32"
+ * Explanation: Replace the substring "1":
+ * - 1 maps to change[1] = 8.
+ * Thus, "<u>1</u>32" becomes "<u>8</u>32".
+ * "832" is the largest number that can be created, so return it.
+ *
+ * Example 2:
+ *
+ * Input: num = "<u>021</u>", change = [9,4,3,5,7,2,1,9,0,6]
+ * Output: "<u>934</u>"
+ * Explanation: Replace the substring "021":
+ * - 0 maps to change[0] = 9.
+ * - 2 maps to change[2] = 3.
+ * - 1 maps to change[1] = 4.
+ * Thus, "<u>021</u>" becomes "<u>934</u>".
+ * "934" is the largest number that can be created, so return it.
+ *
+ * Example 3:
+ *
+ * Input: num = "5", change = [1,4,7,5,3,2,5,6,9,4]
+ * Output: "5"
+ * Explanation: "5" is already the largest number that can be created, so return it.
+ *
+ *  
+ * Constraints:
+ *
+ * 	1 <= num.length <= 10^5
+ * 	num consists of only digits 0-9.
+ * 	change.length == 10
+ * 	0 <= change[d] <= 9
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/largest-number-after-mutating-substring/
+// discuss: https://leetcode.com/problems/largest-number-after-mutating-substring/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn maximum_number(num: String, change: Vec<i32>) -> String {
+        let mut bytes = num.into_bytes();
+
+        bytes
+            .iter_mut()
+            .map(|b| {
+                let new = change[(*b - b'0') as usize] as u8 + b'0';
+                (b, new)
+            })
+            .skip_while(|(b, new)| **b >= *new)
+            .take_while(|(b, new)| **b <= *new)
+            .for_each(|(b, new)| *b = new);
+
+        String::from_utf8(bytes).unwrap()
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1946_example_1() {
+        let num = "132".to_string();
+        let change = vec![9, 8, 5, 0, 3, 6, 4, 2, 6, 8];
+
+        let result = "832".to_string();
+
+        assert_eq!(Solution::maximum_number(num, change), result);
+    }
+
+    #[test]
+    fn test_1946_example_2() {
+        let num = "021".to_string();
+        let change = vec![9, 4, 3, 5, 7, 2, 1, 9, 0, 6];
+
+        let result = "934".to_string();
+
+        assert_eq!(Solution::maximum_number(num, change), result);
+    }
+
+    #[test]
+    fn test_1946_example_3() {
+        let num = "5".to_string();
+        let change = vec![1, 4, 7, 5, 3, 2, 5, 6, 9, 4];
+
+        let result = "5".to_string();
+
+        assert_eq!(Solution::maximum_number(num, change), result);
+    }
+}