大家好，又见面了，我是你们的朋友全栈君。

二叉树层序遍历C语言版

leetcode 102

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */


/**
 * Return an array of arrays of size *returnSize.
 * The sizes of the arrays are returned as *returnColumnSizes array.
 * Note: Both returned array and *columnSizes array must be malloced, assume caller calls free().
 */
 
int** levelOrder(struct TreeNode* root, int* returnSize, int** returnColumnSizes){
    * returnSize = 0;
    * returnColumnSizes = malloc(sizeof(int) * 2010);
    if(root == NULL){
        return 0;
    }
    int i = 0;
    struct TreeNode* node;
    int front=0, top = 0;
    struct TreeNode** q = malloc(sizeof(struct TreeNode*) * 2010);
    int** ret = malloc(sizeof(int*) * 2010);
    q[top++] = root; //q[0] = root
    // 队列为空 top==front
    while(top - front > 0){

        int q_size = top - front;
        (* returnColumnSizes)[i] = q_size;
        ret[i] = malloc(sizeof(int) * q_size);
        for(int j =0; j < q_size;j++){
            node = q[front++]; //出队
            ret[i][j] = node->val;   
            if(node->left != NULL)  q[top++]= node->left;     // push
            if(node->right != NULL)  q[top++]= node->right;
        }
        i++;
    }
    * returnSize = i;
    return ret;

}

挺有意思的