Added RiverSizes.java

CHAUDHARY Shikhar · CHAUDHARY Shikhar · commit 8fd1ea142202 · 2020-05-04T02:53:13.000+01:00
diff --git a/Medium/RiverSizes.java b/Medium/RiverSizes.java
@@ -0,0 +1,99 @@
+package AlgoExpert_Medium;
+
+import java.util.List;
+import java.util.ArrayList;
+
+public class RiverSizes {
+
+	public static void main(String[] args) {
+		
+		int[][] matrix =  { { 1, 0, 0, 1, 0, 1, 0, 0, 1, 1, 1, 0 },
+			                { 1, 0, 1, 0, 0, 1, 1, 1, 1, 0, 1, 0 },
+			                { 0, 0, 1, 0, 1, 1, 0, 1, 0, 1, 1, 1 },
+			                { 1, 0, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0 },
+			                { 1, 0, 1, 1, 0, 0, 0, 1, 1, 1, 0, 1 } 
+			              };
+		
+	System.out.println(riverSizes(matrix));	
+		
+	}
+	
+	  public static List<Integer> riverSizes(int[][] matrix) {
+
+	    int rows = matrix.length;
+		int columns = matrix[0].length ;  // Ask the interviewer whether there is atleast 1 row.
+			
+		boolean[][] visited = new boolean[rows][columns] ; 
+		
+		  List<Integer> list = new ArrayList<>() ; 
+		  
+		for(int i=0 ; i<rows ; i++) {
+			
+			for(int j=0; j< columns ; j++ ) {
+								
+				if(visited[i][j] || matrix[i][j] == 0) {
+					visited[i][j] = true; 
+					continue;
+				}
+				visited[i][j] = true ;
+				int ways = riverSizesRecursion(i, j, matrix, visited) ;
+			 
+				if(ways > 0)
+				list.add(ways) ; 
+			
+			}
+			
+		}
+		
+		  return list;
+	  }
+	  
+		
+	  
+	  // Particular Single Exploration. 
+	  public static int riverSizesRecursion(int row, int column, int[][] matrix, boolean[][] visited) {
+		  		  
+		  // This function calls happens only when matrix[row][column] is equal to 1. 
+		  
+		  int right = 0; 
+		  int size = 1; 
+		  int down = 0 ; 
+		  int left = 0; 
+		  int up = 0 ; 
+		  			  
+		  if(row!=0) { // Up
+			  if(matrix[row-1][column] == 1 && !visited[row-1][column]) {
+				  visited[row-1][column] = true ; 
+				  up = riverSizesRecursion(row-1, column, matrix, visited) ;  //
+			  } 
+		  }
+		  
+		  
+		  if(column!=0) { // Left
+			  if(matrix[row][column-1] == 1 && !visited[row][column-1]) {
+				  visited[row][column-1] = true ; 
+				  left = riverSizesRecursion(row, column-1, matrix, visited) ; 
+			  } 
+		  }
+		  
+		  
+			if(row!=matrix.length-1) { // Down
+			  if(matrix[row+1][column] == 1 && !visited[row+1][column]) {
+				  visited[row+1][column] = true ; 
+				  down = riverSizesRecursion(row+1, column, matrix, visited) ; // 
+			  } 
+		  }	 
+			
+			if(column!=matrix[0].length-1) { // Right
+			  if(matrix[row][column+1] ==1 && !visited[row][column+1]) {
+				  visited[row][column+1] = true; 
+				  right = riverSizesRecursion(row, column+1, matrix, visited) ; 
+			  } 
+			}
+			
+			size = size + up + left + right + down  ; 
+				  
+		  return size; 	  
+	  }
+	  
+}
