# 1432. Max Difference You Can Get From Changing an Integer

## Description

You are given an integer num. You will apply the following steps exactly two times:

• Pick a digit x (0 <= x <= 9).
• Pick another digit y (0 <= y <= 9). The digit y can be equal to x.
• Replace all the occurrences of x in the decimal representation of num by y.
• The new integer cannot have any leading zeros, also the new integer cannot be 0.

Let a and b be the results of applying the operations to num the first and second times, respectively.

Return the max difference between a and b.

Example 1:

Input: num = 555
Output: 888
Explanation: The first time pick x = 5 and y = 9 and store the new integer in a.
The second time pick x = 5 and y = 1 and store the new integer in b.
We have now a = 999 and b = 111 and max difference = 888


Example 2:

Input: num = 9
Output: 8
Explanation: The first time pick x = 9 and y = 9 and store the new integer in a.
The second time pick x = 9 and y = 1 and store the new integer in b.
We have now a = 9 and b = 1 and max difference = 8


Constraints:

• 1 <= num <= 108

## Solutions

• class Solution {
public int maxDiff(int num) {
String a = String.valueOf(num);
String b = a;
for (int i = 0; i < a.length(); ++i) {
if (a.charAt(i) != '9') {
a = a.replace(a.charAt(i), '9');
break;
}
}
if (b.charAt(0) != '1') {
b = b.replace(b.charAt(0), '1');
} else {
for (int i = 1; i < b.length(); ++i) {
if (b.charAt(i) != '0' && b.charAt(i) != '1') {
b = b.replace(b.charAt(i), '0');
break;
}
}
}
return Integer.parseInt(a) - Integer.parseInt(b);
}
}

• class Solution {
public:
int maxDiff(int num) {
auto replace = [](string& s, char a, char b) {
for (auto& c : s) {
if (c == a) {
c = b;
}
}
};
string a = to_string(num);
string b = a;
for (int i = 0; i < a.size(); ++i) {
if (a[i] != '9') {
replace(a, a[i], '9');
break;
}
}
if (b[0] != '1') {
replace(b, b[0], '1');
} else {
for (int i = 1; i < b.size(); ++i) {
if (b[i] != '0' && b[i] != '1') {
replace(b, b[i], '0');
break;
}
}
}
return stoi(a) - stoi(b);
}
};

• class Solution:
def maxDiff(self, num: int) -> int:
a, b = str(num), str(num)
for c in a:
if c != "9":
a = a.replace(c, "9")
break
if b[0] != "1":
b = b.replace(b[0], "1")
else:
for c in b[1:]:
if c not in "01":
b = b.replace(c, "0")
break
return int(a) - int(b)


• func maxDiff(num int) int {
a, b := num, num
s := strconv.Itoa(num)
for i := range s {
if s[i] != '9' {
a, _ = strconv.Atoi(strings.ReplaceAll(s, string(s[i]), "9"))
break
}
}
if s[0] > '1' {
b, _ = strconv.Atoi(strings.ReplaceAll(s, string(s[0]), "1"))
} else {
for i := 1; i < len(s); i++ {
if s[i] != '0' && s[i] != '1' {
b, _ = strconv.Atoi(strings.ReplaceAll(s, string(s[i]), "0"))
break
}
}
}
return a - b
}