链表的查找

题目：https://pintia.cn/problem-sets/15/problems/727

题目设定查找失败返回error 为-1

ElementType FindKth( List L, int K ){
int sum = 0;
while(L!=NULL){
sum++;
if(sum == K){
return L->Data;
}
L = L->Next;
}
return -1;
}