void find(struct TreeNode* root, int* returnSize ,int* result) { if(root->left) find(root->left,returnSize,result); result[(*returnSize)++]=root->val; if(root->right) find(root->right,returnSize,result); } int* inorderTraversal(struct TreeNode* root, int* returnSize ) { if(!root) return NULL; int* result=malloc(sizeof(int)*1000); *returnSize=0; find(root,returnSize,result); return result; }