DEV Community: Ronaldo Peres

Days of Code [4] - Diagonal Traverse

Ronaldo Peres — Fri, 17 Sep 2021 16:48:22 +0000

Hi everyone,

Today I got this problem:

"Given an m x n matrix mat, return an array of all the elements of the array in a diagonal order.
"

Constraints:

m == mat.length
n == mat[i].length
1 <= m, n <= 104
1 <= m * n <= 104
-105 <= mat[i][j] <= 105

The object is to get the numbers in the array going up and down in diagonal.

Example:

Input: mat = [[1,2,3],[4,5,6],[7,8,9]]
Output: [1,2,4,7,5,3,6,8,9]

Another:

Input: mat = [[5,6]]
Output: [5,6]

One more:

Input: mat = [[1,2,3,4],[5,6,7,8]]
Output: [1,2,5,6,3,4,7,8]

Here is one solution:

Diagonal Traverse

Days of Code [3]

Ronaldo Peres — Sun, 12 Sep 2021 19:36:41 +0000

Hi everyone,

Now I have this one:

"You are given a large integer represented as an integer array digits, where each digits[i] is the ith digit of the integer. The digits are ordered from most significant to least significant in left-to-right order. The large integer does not contain any leading 0's.
"

1 Example

Input: digits = [1, 2, 3]
Output: digits = [1, 2, 4]
Explanation: The array represents the integer 123.
Incrementing by one gives 123 + 1 = 124.
Thus, the result should be [1,2,4].

2 Example

Input: digits = [4,3,2,1]
Output: [4,3,2,2]
Explanation: The array represents the integer 4321.
Incrementing by one gives 4321 + 1 = 4322.
Thus, the result should be [4,3,2,2].

3 Example

Input: digits = [9,9,9]
Output: [1,0,0,0]
Explanation: The array represents the integer 99.
Incrementing by one gives 999 + 1 = 1000.
Thus, the result should be [1,0,0,0].

Constraints:

1 <= digits.length <= 100
0 <= digits[i] <= 9
digits does not contain any leading 0's.

Observations

Need to figure out how to solve this one without converting to int or long, since the array can pass the MaxValue, for example:

The int.Maxvalue = 2147483647;

We can have this input:

Input: digits = [9,8,7,6,5,4,3,2,1,0]

So if you think to solve:

Join the array and get a string "9876543210"
When parse it to int we get this, cause we pass the MaxValue:
- System.OverflowException: 'Value was either too large or too small for an Int32.'

Here is my solution:

    public static class PlusOneArray
    {
        public static int[] PlusOne(int[] digits)
        {
            var numOfNine = GetNines(digits);
            if (numOfNine > 0)
            {

                if (digits.Length != numOfNine)
                {
                    digits[digits.Length - numOfNine - 1] += 1;
                }
                else
                {
                    digits[digits.Length - numOfNine] = 1;
                    var newDigits = new int[digits.Length + 1];
                    digits.CopyTo(newDigits, 0);
                    digits = newDigits;
                }

                int i = digits.Length - numOfNine;
                for (; i < digits.Length; i++)
                {
                    digits[i] = 0;
                }
            }
            else
            {
                digits[digits.Length - 1] = digits[digits.Length - 1] + 1;
            }

            return digits;
        }

        private static int GetNines(int[] digits)
        {
            int n = 0;
            for (int i = digits.Length - 1; i >= 0; i--)
            {
                if (digits[i] == 9)
                    n++;
                else
                    break;
            }
            return n;
        }
    }

Also this is at my github:

Peres Github - Plus one

Happy coding!!

Days of code [2]

Ronaldo Peres — Wed, 08 Sep 2021 19:25:01 +0000

The challenge today was this one:

"You are given an integer array nums where the largest integer is unique.
Determine whether the largest element in the array is at least twice as much as every other number in the array. If it is, return the index of the largest element, or return -1 otherwise."

So, to solve this one:

Step by step

Get largest int in the array, lets call this var as 'max'
Get index of largest int in the array
After that, sort the array
And reverse it
With this I created a new array without the first item, cause it was the largest int
Multiply all int by 2 in the new array
Now get the largest number in this new array, lets call this var as newMax
Now check if Max is equal or higher than newMax, if so return tne index that was taken before, if not set result to -1

So, we have:

    public static class LargestNumberInArray
    {
        public static int DominantIndex(int[] nums)
        {
            int result = -1;

            if (nums.Length == 1) return 0;

            // Get largest number and respective index
            int max = nums.Max();
            int tempResult = Array.IndexOf(nums, max);

            Array.Sort(nums);

            // Sort array in desc order and get a new one skipping first number as we know it is the largest
            var arr = nums.Reverse().Select(x => x * 2).ToArray().Skip(1);

            int newMax = arr.Max();

            if (max >= newMax)
            {
                result = tempResult;
            }

            return result;
        }
    }