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 <= 105
num
consists of only digits0-9
.change.length == 10
0 <= change[d] <= 9
Solution: Greedy
Find the first digit that is less equal to the mutated one as the start of the substring, keep replacing as long as mutated >= current.
Time complexity: O(n)
Space complexity: O(1)
C++
1 2 3 4 5 6 7 8 9 10 11 12 13 14 |
// Author: Huahua class Solution { public: string maximumNumber(string num, vector<int>& change) { const int n = num.size(); for (int i = 0; i < n; ++i) if (num[i] - '0' < change[num[i] - '0']) { for (int j = i; j < n && num[j] - '0' <= change[num[j] - '0']; ++j) num[j] = change[num[j] - '0'] + '0'; break; } return num; } }; |
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