LeetCode Entry

1432. Max Difference You Can Get From Changing an Integer

15.06.2025 medium 2025 kotlin rust

Max - min, replacing any digit, no leading zeros

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Problem TLDR

Max - min, replacing any digit, no leading zeros #medium

Intuition

The brute force is fast enough. More optimized:

• max is first non-nine replaced by 9
• min is if first is non-one, replace by 1
• else first non-zero replaced by 0 BUT

Approach

• also can be solved without convertion to strings

Complexity

• Time complexity: \(O(1)\), 10 digits, 10x10 runs, total is 1000 operations; 10 ops for optimized

• Space complexity: \(O(1)\)

Code

// 12ms
    fun maxDiff(n: Int): Int {
        var max = n; var min = n
        for (a in "$n") for (b in "0123456789") {
            val x = "$n".replace(a, b)
            if (x == "0" || x[0] == '0') continue
            max = max(max, x.toInt())
            min = min(min, x.toInt())
        }
        return max - min
    }

// 8ms
    fun maxDiff(n: Int) =
        "$n".replace("$n".find { it != '9' } ?: '.', '9').toInt() -
        if ("$n"[0] > '1') "$n".replace("$n"[0], '1').toInt()
        else "$n".replace("$n".find { it != "$n"[0] && it > '0' } ?: '.', '0').toInt()

// 0ms
    pub fn max_diff(n: i32) -> i32 {
        let (s, mut a, mut b) = (n.to_string(), n, n);
        for c in s.chars() {
            for d in '0'..='9' {
                let x: String = s.chars().map(|x| if x == c { d } else { x }).collect();
                if x == "0" || x.starts_with("0") { continue }
                let x = x.parse().unwrap();
                a = a.max(x); b = b.min(x)
            }
        } a - b
    }

// 0ms
    int maxDiff(int n) {
        string s = to_string(n);
        int a = n, b = n;
        for (char c: s) for (char d = '0'; d <= '9'; ++d) {
            string t = s;
            for (char& x: t) if (x == c) x = d;
            if (t == "0" || t[0] == '0') continue;
            int x = stoi(t); a = max(a, x); b = min(b, x);
        } return a - b;
    }