题解 | 无法吃午餐的学生数量

class Solution {
  public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param students int整型vector
     * @param sandwiches int整型vector
     * @return int整型
     */
    int countStudents(vector<int>& students, vector<int>& sandwiches) {
        // write code here
        deque<int> deq;
        stack<int> st;
        for (int num : students)
            deq.push_back(num);
        for(int i=sandwiches.size()-1;i>=0;i--)
        st.push(sandwiches[i]);
        while (!st.empty()) {
            if (st.top() == deq.front()) {
                st.pop();
                deq.pop_front();
            } else {
                int n = deq.size() - 1,k=0;
                for (int i = 0; i < n; i++) {
                    deq.push_back(deq.front());
                    deq.pop_front();
                    if (st.top() == deq.front()) {
                        st.pop();
                        deq.pop_front();
                        k=1;
                        break;
                    }
                }
                if(k==0)
                return n+1;
            }
        }
        return 0;
    }
};