Commit626f44a

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Create 0145-binary-tree-postorder-traversal

Adding the Java solutions for the Postorder traversal

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	`1`	`+class Solution {`
	`2`	`+ // Iterative`
	`3`	`+ public List<Integer> postorderTraversal(TreeNode root) {`
	`4`	`+ Stack<TreeNode> stack = new Stack<>();`
	`5`	`+ stack.add(root);`
	`6`	`+ Stack<Boolean> visit = new Stack<>();`
	`7`	`+ visit.add(false);`
	`8`	`+`
	`9`	`+ List<Integer> res = new ArrayList<>();`
	`10`	`+`
	`11`	`+ while(!stack.isEmpty()){`
	`12`	`+ TreeNode curr=stack.pop();`
	`13`	`+ boolean v = visit.pop();`
	`14`	`+ if(curr != null){`
	`15`	`+ if(v != false){`
	`16`	`+ res.add(curr.val);`
	`17`	`+ }else{`
	`18`	`+ stack.add(curr);`
	`19`	`+ visit.add(true);`
	`20`	`+ stack.add(curr.right);`
	`21`	`+ visit.add(false);`
	`22`	`+ stack.add(curr.left);`
	`23`	`+ visit.add(false);`
	`24`	`+ }`
	`25`	`+ }`
	`26`	`+ }`
	`27`	`+ return res;`
	`28`	`+ }`
	`29`	`+}`
	`30`	`+`
	`31`	`+class Solution {`
	`32`	`+ // Recursive`
	`33`	`+ public void postorder(TreeNode root, List<Integer> res){`
	`34`	`+ if(root == null) return;`
	`35`	`+`
	`36`	`+ postorder(root.left, res);`
	`37`	`+ postorder(root.right, res);`
	`38`	`+ res.add(root.val);`
	`39`	`+ }`
	`40`	`+ public List<Integer> postorderTraversal(TreeNode root) {`
	`41`	`+ List<Integer> res = new ArrayList<>();`
	`42`	`+`
	`43`	`+ postorder(root, res);`
	`44`	`+ return res;`
	`45`	`+ }`
	`46`	`+}`

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