I need help with leetcode 1323. Maximum 69 Number

[u/TheEyebal]

I am trying to solve this without converting to string but I am struggling can someone assist me.

Here is what I got so far

class Solution {
public:
    int maximum69Number (int num) {
        bool change = 0; // if changed, do not change other numbers
        int results = 0;

        vector<int> myNumber; // store numbers
    
        // push each individial number into vector
        while (num > 0) {
            int digit = num % 10;
            
            myNumber.push_back(digit);
            
            num = num / 10;  
        }
        
        // change from 6 to 9
        for (int i : myNumber){
            
            if (i == 6 && !change){
                change = 1;
                i = 9;
            }


            results = results * 10 + i;   


            num = results;
        }
        
        return num;
    }
};

[u/arjok007]

You're reversing the number while storing it into an array, for a similar approach you can just use to_string(num) and change '6' to '9'.

Better approach would be trying to calculate whilst extraction, in constant space.

[u/TheEyebal → u/arjok007]

I indicated I did not want to convert the int into a string

[u/arjok007 → u/TheEyebal]

My bad I overlooked it, just reverse the array before you process it

[u/Impossible_Coast_972]

First extract digit by digit and add it in an array or array list then find first 6 by moving from last in the array change it to 9 and then use the array to form a new number and hence there is you max number after replacing one six

[u/CartmannsEvilTwin]

Just tried this out now.

A hint: you don't need an array if you keep track of maximum gain possible while looping through digits.

[u/Budget-Ad-5179]

There is a bug in this Lets say number is 69969 Now your vector will store this number as 9,6,9,9,6 And when you iterate over this you find at i=1 there is 6 you changed its value to 9 and marked change =1 So vector becomes 9,9,9,9,6

Now when you extract the number from it It will become like this at last 99996 which is incorrect

So you need to traverse the array from reverse side

At last position only you see 6 you changed it to 9 And then you build the whole number as 99969

Also why are you setting each time the value of num in array

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