//整数,加,减,乘,除,多重小括号表达式的求值，例如 -1+(2-(3+4)/7)*5，(不带输入检查)：#include <sstream>#include <iostream>#include <string>using namespace std;int sToI(string s);string iToS(int myInt);string sCalculate(string s1, string s2, char opr);string nobracket(string s);void main(){    int n, start=0, i;     string s, s1;    cout<<"Input the expression :"<<endl;    cin>>s;                  //例如 -1+(2-(3+4)/7)*5                                 //处理括号：    while(start != -1){              start = -1;        n = s.length();        for(i=0;i<n;i++){            if(s.at(i)==‘(‘){                start = i+1;            }            else if(s.at(i)==‘)‘){                  s1 = nobracket(s.substr(start,i-start));          //处理没有括号的子表达式                s = s.substr(0,start-1) + s1 + s.substr(i+1);  //括号内的值代替原括号及其内容//             cout<<"s = "<<s<<endl;                break;            }        }    }    s = nobracket(s);                         //处理没有括号的整个表达式    cout<<s<<endl;}string nobracket(string s){                //处理没有括号的整个表达式    int start=0, n, i, j, m=0;    char c; string subS[200];    c=s.at(0);    if(c==‘+‘)      s.replace(0,1,"");      //如果表达式最开头有正号，除去它    else if(c==‘-‘) s.replace(0,1,"_");    //如果表达式最开头有负号，用下划线代替它    n = s.length();    for(i=0;i<n;i++){        c=s.at(i);        if(c==‘+‘ || c==‘-‘ || c==‘*‘ || c==‘/‘){            subS[m++]=s.substr(start,i-start);  //把各个数字和运算符分别放到数组 subS[] 单元里            subS[m++]=c;            start=i+1;        }    }    subS[m]=s.substr(start);    i=0;    while(i<m){        c=subS[i].at(0);        if(c==‘*‘ || c==‘/‘){                                 //先乘除             subS[i-1]=sCalculate(subS[i-1], subS[i+1], c);            for(j=i;j<m-1;j++) subS[j]=subS[j+2];            m -= 2;        }        else i++;    }    for(i=1;i<m;i=i+2){                                     //后加减        subS[0]=sCalculate(subS[0], subS[i+1], subS[i].at(0));    }    return subS[0];}string sCalculate(string s1, string s2, char opr){             //计算两字符串得到一个字符串    if(opr==‘+‘) return iToS(sToI(s1)+sToI(s2));    else if(opr==‘-‘) return iToS(sToI(s1)-sToI(s2));    else if(opr==‘*‘) return iToS(sToI(s1)*sToI(s2));    else if(opr==‘/‘) return iToS(sToI(s1)/sToI(s2));    else return "Error opr!";}int sToI(string s){                                                        //字符串转为 int    if(s.at(0)==‘_‘) s.replace(0,1,"-");                              //恢复下划线为负号    istringstream buffer(s); int myInt;    buffer>>myInt;    return myInt;}string iToS(int myInt){                                                 //int 转为字符串    ostringstream buffer;    buffer<<myInt;    return buffer.str();}