题目：

题解：

char** binaryTreePaths(struct TreeNode* root, int* returnSize) {
    char** paths = (char**)malloc(sizeof(char*) * 1001);
    *returnSize = 0;
    if (root == NULL) {
        return paths;
    }

    struct TreeNode** node_queue = (struct TreeNode**)malloc(sizeof(struct TreeNode*) * 1001);
    char** path_queue = (char**)malloc(sizeof(char*) * 1001);

    int left = 0, right = 0;

    char* tmp = malloc(sizeof(char) * 1001);
    sprintf(tmp, "%d", root->val);
    node_queue[right] = root;
    path_queue[right++] = tmp;

    while (left < right) {
        struct TreeNode* node = node_queue[left];
        char* path = path_queue[left++];

        if (node->left == NULL && node->right == NULL) {
            paths[(*returnSize)++] = path;
        } else {
            int n = strlen(path);
            if (node->left != NULL) {
                char* tmp = malloc(sizeof(char) * 1001);
                for (int i = 0; i < n; i++) {
                    tmp[i] = path[i];
                }
                sprintf(tmp + n, "->%d", node->left->val);
                node_queue[right] = node->left;
                path_queue[right++] = tmp;
            }

            if (node->right != NULL) {
                char* tmp = malloc(sizeof(char) * 1001);
                for (int i = 0; i < n; i++) {
                    tmp[i] = path[i];
                }
                sprintf(tmp + n, "->%d", node->right->val);
                node_queue[right] = node->right;
                path_queue[right++] = tmp;
            }
        }
    }
    return paths;
}