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数据栈#xff1a;有数据就直接入栈
运算符栈#xff1a;设遍历到当前的运算符位e#xff0c;如果栈不为空#xff0c;比较栈顶与当前运算符优先级e#xff0c;当栈顶运算符优先级大于或者等于e的优先级#xff0c;则出栈#xff0c;并将两个数据栈的… 原理
数据栈有数据就直接入栈
运算符栈设遍历到当前的运算符位e如果栈不为空比较栈顶与当前运算符优先级e当栈顶运算符优先级大于或者等于e的优先级则出栈并将两个数据栈的数据出栈计算出对应的数据加入到数据栈中否则将运算符入栈
#include iostream
#include unordered_map
#include stack
#include functional
#include string#define MAX_PRI INT_MAXusing namespace std;
int main() {//数据栈stackdouble _data; //运算符栈stackchar _operator; //运算符优先级unordered_mapchar, int pri{ {, 0}, {-, 0}, {*, 1}, {/, 1}, {^, 2}, {(, MAX_PRI }, {), MAX_PRI}};unordered_mapchar, functiondouble(double, double) func{{, [](double x, double y) - double { return x y; }},{-, [](double x, double y) - double { return x - y; }}, {*, [](double x, double y) - double { return x * y; }},{/, [](double x, double y) - double { return x / y; }},{^, [](double x, double y) - double { return pow(x, y); }}};string exp;cin exp;auto calculate [_data, _operator, func]() {char op _operator.top();_operator.pop();double x _data.top();_data.pop();double y _data.top();_data.pop();_data.push(func[op](y, x)); //运算顺序与出栈顺序相反};auto stringtonum [exp, pri](int i) - double {int j i 1;while (j exp.length() pri.find(exp[j]) pri.end()) j;double num stod(exp.substr(i, j - i));i j - 1; return num;};for (int i 0; i exp.length(); i) {char e exp[i];if (pri.find(e) pri.end()) { //当前字符不是运算符则切割数字_data.push(stringtonum(i));} else if (e () {_operator.push(();} else if (e )) {while (_operator.top() ! () {calculate();}_operator.pop();} else {//当前运算符优先级栈顶运算符优先级则出栈计算while (!_operator.empty() pri[_operator.top()] pri[e] _operator.top() ! () {calculate();}_operator.push(e);}}while (!_operator.empty()) {calculate();}cout _data.top() endl;
}
