(排序)链表的插入排序

/*
 * function ListNode(x){
 *   this.val = x;
 *   this.next = null;
 * }
 */

/**
  * 
  * @param head ListNode类 
  * @return ListNode类
  */
function insertionSortList( head ) {
    // write code here
    if(head==null || head.next==null) {
        return head;
    }
    var preHead = new ListNode(-1);
    var curr = head;
    while(curr){
        var pre = preHead;
        var next = curr.next;
        while(pre.next && pre.next.val < curr.val){
            pre = pre.next
        }
        curr.next = pre.next;
        pre.next = curr;
        curr = next;
    }
    return preHead.next;
}
module.exports = {
    insertionSortList : insertionSortList
};