Brick Wall.java

// Runtime: 16 ms (Top 21.1%) | Memory: 46.16 MB (Top 61.8%)

class Solution {
    public int leastBricks(List<List<Integer>> wall) 
    {
        HashMap<Integer, Integer> edge_frequency = new HashMap<>(); //HashMap to store the number of common edges among the rows
        int max_frequency = 0; //Variable to store the frequency of most occuring edge
        
        for(int row=0; row<wall.size(); row++) //Iterating through each row
        {
            int edge_postion = 0; //Variable to store different edge postion
            
            for(int brick_no=0; brick_no<wall.get(row).size()-1; brick_no++) //Iterating through each brick inside a row
            {
                int current_brick_length = wall.get(row).get(brick_no); //Length of the current brick
                edge_postion = edge_postion + current_brick_length; //Next Edge Position = Previous Edge Position + Current Brick's Length
                edge_frequency.put(edge_postion,edge_frequency.getOrDefault(edge_postion,0)+1); //Incrementing the Frequency of just calculated Edge Postion
                max_frequency = Math.max(edge_frequency.get(edge_postion),max_frequency); //Comparing the "Frequency of just calculated Edge Postion" with "Max Frequency seen till now" & storing whichever is greater.
            }
        }
        return wall.size() - max_frequency; // returning (Number of Bricks Crossed by Line) i.e. (Number of Rows in Wall - Frequency of Most Occuring Edge)
    }
}