108 convert sorted array to bina

递归实现：
数组中间节点做为根节点， 然后把左边的数组递归赋予左子树，右边数组递归赋予右子树

struct TreeNode* sortedArrayToBST(int* nums, int numsSize) {
    if(nums == NULL || numsSize == 0)
        return NULL;

    int mid = (numsSize-1)/2;
    int val = nums[mid];
    struct TreeNode * node = calloc(1, sizeof(struct TreeNode));
    node->val = val;
    node->right = sortedArrayToBST(nums+mid+1,numsSize-mid-1);
    node->left = sortedArrayToBST(nums,mid);

    return node;
}