LeetCode in Kotlin
1946. Largest Number After Mutating Substring
Medium
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 = “132”, change = [9,8,5,0,3,6,4,2,6,8]
Output: “832”
Explanation: Replace the substring “1”:
- 1 maps to change[1] = 8. Thus, “132” becomes “832”.
“832” is the largest number that can be created, so return it.
Example 2:
Input: num = “021”, change = [9,4,3,5,7,2,1,9,0,6]
Output: “934”
Explanation: Replace the substring “021”:
-
0 maps to change[0] = 9.
-
2 maps to change[2] = 3.
-
1 maps to change[1] = 4.
Thus, “021” becomes “934”.
“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 <= 105numconsists of only digits0-9.change.length == 100 <= change[d] <= 9
Solution
class Solution {
fun maximumNumber(num: String, change: IntArray): String {
val n = num.length
val nums = num.toCharArray()
val arr = CharArray(n)
for (i in 0 until n) {
val `val` = nums[i].code - '0'.code
arr[i] = (change[`val`] + '0'.code).toChar()
}
var flag = false
for (i in 0 until n) {
if (nums[i] < arr[i]) {
nums[i] = arr[i]
flag = true
} else if (flag && nums[i] > arr[i]) {
break
}
}
return String(nums)
}
}