Not able to find the largest area

#1

My approach for this question is that I made a landscape matrix (2-D) of size [max of x axis] [ max of y axis] ( x and y that are input by user). Then in the lanscape matrix, I have searched for rows and columns matching with the co-ordinates input by user, then I changed the values of those rows and columns to 1 from 0 which is default. In this way , the maximum area is largest sub-matrix inside landscape array having only 0 as element but I am not able to write code to find the largest sub-matrix

#2

import java.util.Scanner; public class GrandTemple { public static void main(String[] args) { Scanner sc = new Scanner(System.in); int n = sc.nextInt(); int[] arr = new int[n]; int[] brr = new int[n]; for (int i = 0; i < n; i++) { arr[i] = sc.nextInt(); brr[i] = sc.nextInt(); } int a = max(arr); int b = max(brr); int[][]landscape=new int[a+1][b+1]; for(int i =0;i<landscape.length;i++) { for(int j =0;j<landscape[i].length;j++) { for(int k =0;k<arr.length;k++) { if(i==arr[k] || j==brr[k]) { landscape[i][j]=1; } } } } int[]count=new int[a*b]; } public static int max(int[] arr) { int max = Integer.MIN_VALUE; for (int i = 0; i < arr.length; i++) { if (arr[i] > max) { max = arr[i]; } } return max; } }

#3

@Syed-Siddiqui-2497215583854102,

You have to maximise the area obtained between the rivers. Since the intersection points of rivers are provided to you as input , you need to find the largest consecutive gap between the x coordinates and y coordinates.
This problem falls under the Greedy Algorithms section. A very similar problem ( practically the same ) is covered in the Greedy Algorithms tutorial video as well.
You need to implement a greedy algorithm for this problem.
Take the x coordinates input in an array , say X .
Take the y coordinates input in an array , say Y .
We need to find the maximum area. We can obtain it by finding the largest gap in the x coordinates and multiplying with the largest gap in the y coordinates.
So just do that , find the maximum gap between consecutive x coordinates in the X array and do the same for Y.
Multiply these maximum gaps and you will have your maximum area.
Hint : Sorting might help.

This is a pretty simple problem. All we need to do is just store all the X and Y coordinates and then sort them. Then we will calculate maximum ΔX and ΔY where ΔX = (Xi -X(i-1)) & ΔY = (Yi -Y(i-1)).

Then the area will be (ΔY-1)*(ΔX-1)

#4

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