1946. Largest Number After Mutating Substring

Description

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 digits 0-9.
  • change.length == 10
  • 0 <= change[d] <= 9

Solutions

Solution 1

Python Code
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class Solution:
    def maximumNumber(self, num: str, change: List[int]) -> str:
        s = list(num)
        for i, c in enumerate(s):
            if change[int(c)] > int(c):
                while i < len(s) and int(s[i]) <= change[int(s[i])]:
                    s[i] = str(change[int(s[i])])
                    i += 1
                break
        return ''.join(s)

Java Code
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class Solution {
    public String maximumNumber(String num, int[] change) {
        char[] s = num.toCharArray();
        for (int i = 0; i < s.length; ++i) {
            if (change[s[i] - '0'] > s[i] - '0') {
                for (; i < s.length && s[i] - '0' <= change[s[i] - '0']; ++i) {
                    s[i] = (char) (change[s[i] - '0'] + '0');
                }
                break;
            }
        }
        return String.valueOf(s);
    }
}

C++ Code
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class Solution {
public:
    string maximumNumber(string num, vector<int>& change) {
        int n = num.size();
        for (int i = 0; i < n; ++i) {
            if (change[num[i] - '0'] > num[i] - '0') {
                for (; i < n && change[num[i] - '0'] >= num[i] - '0'; ++i) {
                    num[i] = change[num[i] - '0'] + '0';
                }
                break;
            }
        }
        return num;
    }
};

Go Code
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func maximumNumber(num string, change []int) string {
	s := []byte(num)
	for i, c := range num {
		if change[c-'0'] > int(c-'0') {
			for ; i < len(s) && change[s[i]-'0'] >= int(s[i]-'0'); i++ {
				s[i] = byte(change[s[i]-'0']) + '0'
			}
			break
		}
	}
	return string(s)
}