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BottomViewOfTree.java
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51 lines (43 loc) · 1.45 KB
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package Leetcode;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.PriorityQueue;
public class BottomViewOfTree
{
public static List<Integer> topView( TreeNode root )
{
HashMap<Integer, Integer> map = new HashMap<>();
viewHelper( root, map, 0 );
PriorityQueue<Integer> minHeap = new PriorityQueue<Integer>( ( a, b ) -> a - b );
for( Integer key : map.keySet() )
{
minHeap.add( key );
}
List<Integer> sortedResult = new ArrayList();
while( !minHeap.isEmpty() )
sortedResult.add( map.get( minHeap.remove() ) );
return sortedResult;
}
private static void viewHelper( TreeNode root, HashMap<Integer, Integer> map, int level )
{
if( root == null )
return;
map.put( level, root.val );
viewHelper( root.left, map, level - 1 );
viewHelper( root.right, map, level + 1 );
}
public static void main( String[] args )
{
TreeNode root = new TreeNode( 1 );
root.left = new TreeNode( 2 );
root.right = new TreeNode( 3 );
root.left.left = new TreeNode( 4 );
root.left.right = new TreeNode( 5 );
root.right.left = new TreeNode( 6 );
root.right.right = new TreeNode( 7 );
List<Integer> result = BottomViewOfTree.topView( root );
for( Integer number : result )
System.out.println( number );
}
}