PAT 3-05. 求链式线性表的倒数第K项

题目地址：http://pat.zju.edu.cn/contests/ds/3-05

用vector有一个case超时，用list 顺利通过

#include<cstdio>#include<list>using namespace std;int main(){    int K, num;    list<int> vec;    scanf("%d", &K);    while(scanf("%d", &num) && num>=0)    {        vec.push_back(num);    }    if(int(vec.size()-K)>=0)    {        list<int>::reverse_iterator it = vec.rbegin();        --K;        while(K)        {            --K;            it++;        }        printf("%d\n", *it);    }    else    {        printf("NULL\n");    }    return 0;}