Given a binary tree, return the preorder traversal of its nodes‘ values.
For example:
Given binary tree {1,#,2,3}
,
1 2 / 3
return [1,2,3]
.
Note: Recursive solution is trivial, could you do it iteratively?
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解答
注意空树的情况……
/** * Definition for a binary tree node. * struct TreeNode { * int val; * struct TreeNode *left; * struct TreeNode *right; * }; */ /** * Return an array of size *returnSize. * Note: The returned array must be malloced, assume caller calls free(). */ int* preorderTraversal(struct TreeNode* root, int* returnSize) { int top = -1, i = 0; int *return_array = (int*)malloc(sizeof(int) * 1000); struct TreeNode *stack[1000]; if(NULL == root){ *returnSize = i; return return_array; } stack[++top] = root; while(-1 != top){ root = stack[top--]; return_array[i++] = root->val; if(NULL != root->right) stack[++top] = root->right; if(NULL != root->left) stack[++top] = root->left; } *returnSize = i; return return_array; }
时间: 2024-11-08 23:49:20