class Solution {
public:
    bool validateStackSequences(vector<int>& pushed, vector<int>& popped) {
        stack<int> st;
        for(int i=0,j=0;i<pushed.size();i++){
            st.push(pushed[i]);
            while(!st.empty()&&st.top()==popped[j]){
                st.pop();
                j++;
            }
        }
        return st.empty();
    }
};