"Binary Tree Inorder Traversal"

Author: lennylxx

src/94.c

@@ -0,0 +1,101 @@
+#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 *inorderTraversal(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;
+    while (stack.size || p) {
+        if (p) {
+            push(&stack, p);
+            p = p->left;
+        }
+        else {
+            p = top(stack);
+            pop(&stack);
+            ret[(*returnSize)++] = p->val;
+            p = p->right;
+        }
+    }
+    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 = inorderTraversal(p, &size);
+    int i;
+    /* should be 12345 */
+    for (i = 0; i < size; i++) {
+        printf("%d", ret[i]);
+    }
+    printf("\n");
+
+    return 0;
+}