C++四则计算器源码

来源：互联网发布：淘宝阿里旺旺号那里看编辑：程序博客网时间：2024/05/17 08:39

我建议每个像我一样的小白，都自己动手写一下，四则计算器，因为这里面既有队列的知识，又有栈的知识，又有字符串处理的知识，而且还可以对自己的逻辑思维进行一定强度的锻炼，可以说有百利而无一害！我这里写的代码仅供大家参考，因为比较简单我也没怎么写注释。talking is cheapshow me the code

#include <iostream>#include <queue>#include <stack>using namespace std;const int INF=1000;//调度场算法 中缀表达式转后缀表达式template <typename T> queue<T>& dispatch(pair<T,int> infix[],long size){    //var can't use to convert type,but we can use it to define a type;    stack<pair<T, int>> operators;    queue<T>* result=new queue<T>;    for (int i=0; i<size; i++) {        if (infix[i].second==0) {//if it is a number;            result->push(infix[i].first);        }else if(infix[i].second!=INF){//or it is a operator;            if(operators.empty()){               operators.push(infix[i]);            }else if(infix[i].second>operators.top().second){                operators.push(infix[i]);            }else{                do{                    result->push(operators.top().first);                    operators.pop();                } while (!operators.empty()&&infix[i].second<=operators.top().second);                                operators.push(infix[i]);                        }                }            }    while(!operators.empty()){        result->push(operators.top().first);        operators.pop();    }       return *result;}//创建带有优先级的操作符pairpair<string, int>* init_infix_pair(vector<string> infix,long size) {    pair<string, int>* opers=new pair<string,int>[size];    int current_priority=1;    for (int i=0; i<size; i++) {        pair<string,int> oper(infix[i],0);        if(infix[i]=="("){current_priority+=2;oper.second=INF;}        else if(infix[i]==")"){current_priority-=2;oper.second=INF;}        else if(infix[i]=="*"||infix[i]=="/"){            oper.second=current_priority+1;        }else if(infix[i]=="+"||infix[i]=="-"){            oper.second=current_priority;        }        opers[i]=oper;    }    return opers;}//把字符串转换成字符串数组,以运算符作为分隔符,可以处理小数点vector<string>&  convert_string_to_array(string exp){    int start,end;    vector<string>* vec=new vector<string>;    for (int i=0; i<exp.size(); i++) {        if(exp[i]>='0'&&exp[i]<='9'){            if(!isdigit(exp[i-1])&&exp[i-1]!='.'){                start=i;            }        }else{            if(exp[i]=='.')continue;            if(i==0||!isdigit(exp[i-1])){               vec->push_back(exp.substr(i,1));            }            else{                end=i;                vec->push_back(exp.substr(start,end-start));                vec->push_back(exp.substr(i,1));            }                    }    }    return *vec;}//构建一个vector,元素为pair,first标识是数字还是运算符,second为具体内容vector< pair<bool, double> >& convert_queue_to_vector(queue<string> result){    vector<pair<bool,double>>* vec=new vector<pair<bool,double>>;    while(!result.empty()){               char oper=*result.front().c_str();        if(oper=='+'||oper=='-'||oper=='*'||oper=='/'){            vec->push_back(pair<bool,double>(true,oper));            result.pop();            continue;        }        vec->push_back(pair<bool,double>(false,atof(result.front().c_str())));        result.pop();    }    return *vec;}//利用栈计算后缀表达式double caculate_string_vector(vector<pair<bool, double>> vec){    stack<double> result_stack;    for (int i=0; i<vec.size(); i++) {        if(vec[i].first==false){            result_stack.push(vec[i].second);        }else{                    double TF,TS;            double result;            TF=result_stack.top();            result_stack.pop();            TS=result_stack.top();            result_stack.pop();            if(vec[i].second=='+')                result=TS+TF;            if(vec[i].second=='-')                result=TS-TF;            if(vec[i].second=='*')                result=TS*TF;            if(vec[i].second=='/')                result=TS/TF;            result_stack.push(result);                                        }        }    return result_stack.top();}int main(){     string exp="(123.0+(45.75-20*(10-9)))*56.23+(3.2-100)";    vector<string>& vec=convert_string_to_array(exp);    vector<string>::iterator it=vec.begin();    while (it!=vec.end()) {        cout<<*it<<" ";        it++;    }    cout<<endl;    pair<string,int>* ps=init_infix_pair(vec,vec.size());    queue<string>& result=dispatch(ps,vec.size());        vector< pair<bool,double> >& final=convert_queue_to_vector(result);    cout<< caculate_string_vector(final)<<endl;    while(!result.empty()){        cout<<result.front()<<" ";        result.pop();    }    cout<<endl;    return 0;}