二叉树遍历算法（递归实现先序中序和后续遍历）（非递归实现中序和先续）

二叉树遍历

递归实现

void RecursionBackTree(TreeNode * root) {
if (root) {
//先续遍历
//cout << root->val << " ";
RecursionBackTree(root->left);
//中续遍历
//cout << root->val << " ";
RecursionBackTree(root->right);
//后续遍历
cout << root->val << " ";
}
}

迭代版本

先序遍历

//Preorder
void IterateFirstTraverse(TreeNode* root) {
if (!root) return;
stack<TreeNode*>  st;
while (true) {
while (root) {
cout << root->val<<" ";
st.push(root->right);
root = root->left;
}
if (!st.empty()) {
root = st.top();
st.pop();
}
else {
break;
}
}
cout << endl;
}

中序遍历

void IterateTraverse(TreeNode* root) {
if (!root) return;
stack<TreeNode* > st;
//st.push(root);
//root = root->left;
while (true) {
while (root) { st.push(root); root = root->left; }
if (st.empty()) break;
root = st.top();
st.pop();
cout << root->val<<" ";
root = root->right;
}
cout << endl;
}