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Update 107-Binary-Tree-Level-Order-Traversal-II.java

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Lines changed: 3 additions & 8 deletions

Original file line number	Diff line number	Diff line change
`@@ -1,5 +1,6 @@`
`1`		`-//Same just reverse in the end.`
	`1`	`+//Same just reverse in the end.`
`2`	`2`	`//Reversing in the end is better than using add(0, E) in case of arraylist as it's an O(1) operation.`
	`3`	`+`
`3`	`4`	`classSolution {`
`4`	`5`	`publicList<List<Integer>>levelOrderBottom(TreeNoderoot) {`
`5`	`6`	`List<List<Integer>>ans =newArrayList<>();`
`@@ -19,13 +20,7 @@ public List<List<Integer>> levelOrderBottom(TreeNode root) {`
`19`	`20`	`}`
`20`	`21`	`inti =0 ,j =ans.size()-1;`
`21`	`22`	`//reverse the list`
`22`		`-while (i<j) {`
`23`		`-List<Integer>cur =ans.get(i);`
`24`		`-ans.set(i,ans.get(j));`
`25`		`-ans.set(j,cur);`
`26`		`-i++;`
`27`		`-j--;`
`28`		`- }`
	`23`	`+Collections.reverse(ans);`
`29`	`24`	`returnans;`
`30`	`25`	`}`
`31`	`26`	`}`

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