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bool validateStackSequences(vector<int>& pushed, vector<int>& popped) {
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    stack<int> st;
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    int i = 0;
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    for(auto &t: popped) {
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        if (!st.empty() && st.top() == t) {
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            st.pop();
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        } else {
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            while(i < pushed.size() && pushed[i] != t) {
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                st.push(pushed[i]);
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                i++;
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            }
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            if (pushed.size() == i) return false;
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            i++;
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        }
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    }
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    return true;
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}