二叉树的遍历

 

 

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class TreeNode {         int val = 0;         TreeNode left = null;         TreeNode right = null;           public TreeNode(int val) {             this.val = val;         }     }

前序遍历

    递归版

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private void getPreTree(TreeNode node, List<Integer> list) {       if (node == null) {           return;       }       //zhong 左右       list.add(node.val);       if (node.left != null) {           getPreTree(node.left, list);       }       if (node.right != null) {           getPreTree(node.right, list);       }   }

　　

中序遍历

    递归版

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private void getMidTree(TreeNode node, List<Integer> list) {         if (node == null) {             return;         }           //左中右         if (node.left != null) {             getMidTree(node.left, list);         }         list.add(node.val);         if (node.right != null) {             getMidTree(node.right, list);         }     }

　　

后序遍历

    递归版

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private void getAfterTree(TreeNode node, List<Integer> list) {       if (node == null) {           return;       }         //左右中       if (node.left != null) {           getAfterTree(node.left, list);       }       if (node.right != null) {           getAfterTree(node.right, list);       }       list.add(node.val);   }