[Problems] Summary of Problems on Arrays

  1. Find all pairs of integers within an array that sum to a specified value:

    • Approach 1: Using hash table (more time efficient)

    • Approach 2: Through sorting (more space efficient)

  2. Given an M x N matrix, if an element is 0, its entire row and column in the matrix should be set to 0.

  3. You are given a 2-Dimensional array (matrix) and a scale factor. You need to write a method to scale the 2D array according to the scale factor.

    1. The signature of the method should be 

      1. public static int[][] scale1(int[][] arr, int scale)

    2. Example: if you are given a 2*3 array and scale factor is 3, the output array will be 6*9; the input and output arrays will be as follows:

      • Input

        • 1 2 3 

        • 4 5 6 

      • Output

        • 1 1 1 2 2 2 3 3 3 

        • 1 1 1 2 2 2 3 3 3 

        • 1 1 1 2 2 2 3 3 3 

        • 4 4 4 5 5 5 6 6 6 

        • 4 4 4 5 5 5 6 6 6 

        • 4 4 4 5 5 5 6 6 6 

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