逆波兰表达式生成算法是比较当前运算符与栈顶运算符的优先关系，若当前运算符的优先级高于栈顶运算符，则当前运算符入栈，若当前运算符的优先级低于栈顶运算符，则栈顶运算符退栈。-Reverse Polish expression generation algorithm is more current operator and the operator stack ranking, if the current operator precedence than the stack operator, then the current operator stack, if the current operator precedence than stack operator, the operator back stack stack.