Max Difference You Can Get From Changing an Integer

This problem is just yesterdays problem but with more test cases to check for.

This solution is just yesterdays solution but with an extra test-case; since to find the max difference, both numbers cannot have a leading 0, it implies that to find the minimum value, we either have to:

• if the first digit is not 1
  • then we can convert all instances of that digit to 1
• else, the first digit is 1 and we iterate through the string to find the first instance of a digit that is NOT 1 or 0
  • then we can convert all instances of that digit to 0

code

class Solution {
public:
    int maxDiff(int num) {
        string maxAns = to_string(num);
        string minAns = to_string(num);
        int i = 0;
        char maxTemp = '-';
        char minTemp = '-';
        char toReplace;
        for (; i < maxAns.size() && (maxTemp == '-' || minTemp == '-'); ++i) {
            if (maxTemp == '-' && maxAns[i] != '9') {
                maxTemp = maxAns[i];
                maxAns[i] = '9';
            } else if (maxTemp == maxAns[i]) {
                maxAns[i] = '9';
            }
            if (minTemp == '-' && i == 0 && minAns[i] != '1') {
                minTemp = minAns[i];
                toReplace = '1';
                minAns[i] = toReplace;
            } else if (minTemp == '-' && minAns[i] != '1' && minAns[i] != '0') {
                minTemp = minAns[i];
                toReplace = '0';
                minAns[i] = toReplace;
            } else if (minTemp == minAns[i]) {
                minAns[i] = toReplace;
            }
        }
        for (; i < maxAns.size(); ++i) {
            if (maxTemp == maxAns[i]) {
                maxAns[i] = '9';
            }
            if (minTemp == minAns[i]) {
                minAns[i] = toReplace;
            }
        }
        return stoi(maxAns) - stoi(minAns);
    }
};

complexity

• Time: O(log(n)) where n is num
• Space: O(log(n))

learnings

• you can do it with O(1) space complexity by using math

time taken

• 5 minutes and 56 seconds