题解 | #栈的压入、弹出序列#

class Solution {
  private:
    bool isBehind(int pushIndex, int popNum, std::vector<int>& pushV) {
        bool result = false;
        for (int j = pushIndex; j < pushV.size(); j++) {
            if (pushV[j] == popNum) result = true; // 在index位置的后面
        }
        return result;
    }
  public:
    bool IsPopOrder(std::vector<int>& pushV, std::vector<int>& popV) {
        if (popV.size() == 0 || pushV.size() == 0) return false;

        std::stack<int> stack;
        int pushIndex = 0;
        int temp = 0;

        for (int i = 0; i < popV.size(); i++) {
            int popNum = popV[i];
            if (stack.empty() || stack.top() != popNum) {
                if (isBehind(pushIndex, popNum, pushV)) {
                    while (pushV[pushIndex] != popNum) { // 将相应的值压入堆栈
                        stack.push(pushV[pushIndex]);
                        pushIndex++;
                    }
                } else return false;
                pushIndex++;
            }
			else if (stack.top() == popNum) {
                stack.pop();
            }
        }
        return true;
    }
};