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| #include <bits/stdc++.h>
#define DBG(x) cerr << #x << " = " << x << endl
using namespace std;
typedef long long LL;
struct Node {
int val;
Node *left, *right;
Node() : left(NULL), right(NULL) {}
Node(int val) : val(val), left(NULL), right(NULL) {}
};
enum StackState {
AFTER_PUSH_ROOT = 0,
AFTER_PUSH_LEFT = 1,
AFTER_PUSH_RIGHT = 2,
};
void dfs_pre_order(Node *root, vector<int> &ret) {
ret.push_back(root->val);
if (root->left) dfs_pre_order(root->left, ret);
if (root->right) dfs_pre_order(root->right, ret);
}
void dfs_in_order(Node *root, vector<int> &ret) {
if (root->left) dfs_in_order(root->left, ret);
ret.push_back(root->val);
if (root->right) dfs_in_order(root->right, ret);
}
void dfs_post_order(Node *root, vector<int> &ret) {
if (root->left) dfs_post_order(root->left, ret);
if (root->right) dfs_post_order(root->right, ret);
ret.push_back(root->val);
}
void pre_order(Node *root, vector<int> &ret) {
stack<pair<Node *, StackState>> stk;
stk.push(pair<Node *, StackState>(root, AFTER_PUSH_ROOT));
while (!stk.empty()) {
pair<Node *, StackState> &top = stk.top();
switch (top.second) {
case AFTER_PUSH_ROOT:
ret.push_back(top.first->val);
if (top.first->left) stk.push(pair<Node *, StackState>(top.first->left, AFTER_PUSH_ROOT));
top.second = AFTER_PUSH_LEFT;
break;
case AFTER_PUSH_LEFT:
if (top.first->right) stk.push(pair<Node *, StackState>(top.first->right, AFTER_PUSH_ROOT));
top.second = AFTER_PUSH_RIGHT;
break;
case AFTER_PUSH_RIGHT:
stk.pop();
break;
}
}
}
void in_order(Node *root, vector<int> &ret) {
stack<pair<Node *, StackState>> stk;
stk.push(pair<Node *, StackState>(root, AFTER_PUSH_ROOT));
while (!stk.empty()) {
pair<Node *, StackState> &top = stk.top();
switch (top.second) {
case AFTER_PUSH_ROOT:
if (top.first->left) stk.push(pair<Node *, StackState>(top.first->left, AFTER_PUSH_ROOT));
top.second = AFTER_PUSH_LEFT;
break;
case AFTER_PUSH_LEFT:
ret.push_back(top.first->val);
if (top.first->right) stk.push(pair<Node *, StackState>(top.first->right, AFTER_PUSH_ROOT));
top.second = AFTER_PUSH_RIGHT;
break;
case AFTER_PUSH_RIGHT:
stk.pop();
break;
}
}
}
void post_order(Node *root, vector<int> &ret) {
stack<pair<Node *, StackState>> stk;
stk.push(pair<Node *, StackState>(root, AFTER_PUSH_ROOT));
while (!stk.empty()) {
pair<Node *, StackState> &top = stk.top();
switch (top.second) {
case AFTER_PUSH_ROOT:
if (top.first->left) stk.push(pair<Node *, StackState>(top.first->left, AFTER_PUSH_ROOT));
top.second = AFTER_PUSH_LEFT;
break;
case AFTER_PUSH_LEFT:
if (top.first->right) stk.push(pair<Node *, StackState>(top.first->right, AFTER_PUSH_ROOT));
top.second = AFTER_PUSH_RIGHT;
break;
case AFTER_PUSH_RIGHT:
ret.push_back(top.first->val);
stk.pop();
break;
}
}
}
Node *get_tree(int num) {
Node *root = new Node(random());
vector<Node *> nodes;
nodes.push_back(root);
for (int i = 0; i < num; i++) {
unsigned int pos = random() * random() * random() % nodes.size();
if (nodes[pos]->left == NULL && nodes[pos]->right == NULL) {
if (random() % 2 == 0) {
nodes[pos]->left = new Node(random());
nodes.push_back(nodes[pos]->left);
} else {
nodes[pos]->right = new Node(random());
nodes.push_back(nodes[pos]->right);
}
} else if (nodes[pos]->left) {
nodes[pos]->right = new Node(random());
nodes.push_back(nodes[pos]->right);
} else {
nodes[pos]->left = new Node(random());
nodes.push_back(nodes[pos]->left);
}
if (nodes[pos]->left && nodes[pos]->right) {
nodes.erase(nodes.begin() + pos);
}
}
return root;
}
void free_tree(Node *root) {
if (root->left) free_tree(root->left);
if (root->right) free_tree(root->right);
delete root;
}
void test_pre_order() {
Node *tree = get_tree(100000);
vector<int> dfs_ret, ret;
dfs_pre_order(tree, dfs_ret);
pre_order(tree, ret);
assert(dfs_ret == ret);
free_tree(tree);
}
void test_in_order() {
Node *tree = get_tree(100000);
vector<int> dfs_ret, ret;
dfs_in_order(tree, dfs_ret);
in_order(tree, ret);
assert(dfs_ret == ret);
free_tree(tree);
}
void test_post_order() {
Node *tree = get_tree(100000);
vector<int> dfs_ret, ret;
dfs_post_order(tree, dfs_ret);
post_order(tree, ret);
assert(dfs_ret == ret);
free_tree(tree);
}
int main(int argc, char **argv) {
srand(time(NULL));
test_pre_order();
test_in_order();
test_post_order();
return 0;
}
|