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145.c
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145.c
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#include <stdio.h>
#include <stdlib.h>
struct TreeNode {
int val;
struct TreeNode *left;
struct TreeNode *right;
};
struct StackNode {
struct TreeNode *val;
struct StackNode *next;
};
struct Stack {
struct StackNode *top_pt;
int size;
};
void push(struct Stack *stack, struct TreeNode *new_data) {
if (stack) {
struct StackNode *new_node
= (struct StackNode *)calloc(1, sizeof(struct StackNode));
new_node->val = new_data;
new_node->next = stack->top_pt;
stack->top_pt = new_node;
stack->size++;
}
}
struct TreeNode* top(struct Stack stack) {
if (stack.top_pt) {
return stack.top_pt->val;
}
else return NULL;
}
void pop(struct Stack *stack) {
if (stack && stack->top_pt) {
struct StackNode *top = stack->top_pt;
stack->top_pt = top->next;
stack->size--;
free(top);
}
}
int *postorderTraversal(struct TreeNode *root, int *returnSize) {
*returnSize = 0;
if (root == NULL) return NULL;
struct Stack stack;
stack.top_pt = NULL;
stack.size = 0;
int *ret = (int *)calloc(1024, sizeof(int));
struct TreeNode *p = root;
struct TreeNode *last = NULL;
while (stack.size || p) {
if (p) {
push(&stack, p);
p = p->left;
}
else {
struct TreeNode *t = top(stack);
if (t->right && last != t->right) {
p = t->right;
}
else {
pop(&stack);
ret[(*returnSize)++] = t->val;
last = t;
}
}
}
return ret;
}
int main() {
struct TreeNode *t = (struct TreeNode *)calloc(5, sizeof(struct TreeNode));
struct TreeNode *p = t;
p->val = 4;
p->left = ++t;
t->val = 2;
p->left->left = ++t;
t->val = 1;
t->left = t->right = NULL;
p->left->right = ++t;
t->val = 3;
t->left = t->right = NULL;
p->right = ++t;
t->val = 5;
t->left = t->right = NULL;
int size = 0;
int *ret = postorderTraversal(p, &size);
int i;
/* should be 13254 */
for (i = 0; i < size; i++) {
printf("%d", ret[i]);
}
printf("\n");
return 0;
}