题目要求:

写一个函数StrToInt实现将字符串转换为整数的功能。　

需要考虑的点

• 字符串为空串或空指针.
• 字符串含有非0到9的字符.
• 特别注意字符串转换到int值,要考虑溢出的问题,正整数的最大值是0x7FFFFFFF,负数的最小值是0x80000000.

代码如下:

#include<iostream>#include<string.h>#include<limits>bool strToInt(constchar *str,int &nInt){if(str == NULL){std::cout <<"空指针"<<std::endl;returnfalse;    }elseif(str ==""){std::cout <<"空串"<<std::endl;returnfalse;    }elseif((strcmp(str,"+") ==0) || (strcmp(str,"-") ==0)){std::cout <<"字符串输入无效"<<std::endl;returnfalse;    }else{constchar *p = str;bool isFirst =true;//标记是否为字符串的第一个字符bool hasMinus =false;//标记字符串的第一个字符是否是负号.        nInt =0;while(*p !='\0'){if(isFirst && (*p) =='-' ){                hasMinus =true;                p++;continue;            }elseif(isFirst && (*p) =='+'){                p++;continue;            }if((*p) >='0' && (*p) <='9'){                nInt = nInt*10+*p-'0';if((!hasMinus && nInt >std::numeric_limits<int>::max()) || (hasMinus && nInt <std::numeric_limits<int>::min())){std::cout <<"字符串数值溢出,输入无效!"<<std::endl;returnfalse;                }                    p++;                }else{std::cout <<"字符串中包含有非数字的字符,不能转换为数字"<<std::endl;returnfalse;                }        }if(hasMinus){                        nInt = (-1) * nInt;                    }returntrue;    }}int main(int argc,char *argv[]){int nInt =0;char *str = NULL;if(strToInt("123",nInt)){std::cout << nInt<<std::endl;    }if(strToInt("",nInt)){std::cout <<nInt<<std::endl;    }if(strToInt(str,nInt)){std::cout <<nInt<<std::endl;    }if(strToInt("-123",nInt)){std::cout <<nInt<<std::endl;    }if(strToInt("+123",nInt)){std::cout <<nInt<<std::endl;    }if(strToInt("-#45466@",nInt)){std::cout <<nInt<<std::endl;    }if(strToInt("10000000000000000000000000",nInt)){std::cout <<nInt<<std::endl;    }if(strToInt("-10000000000000000000000000",nInt)){std::cout <<nInt<<std::endl;    }return0;}