C++判断字符串是否为数字

思路1：挨个字符判断其ASCII码是否属于数字范围 48--57

转为ASC码 ：int i=(int)a; //a是字符

string s;

int tmp = (int)s[i];

思路二

C++实例：

#include <iostream>#include <sstream>using namespace std;bool isNum(string str);int main( ){string ss1="2y5r";string ss2="2558";if(isNum(ss1)){cout<<"ss1 is a num"<<endl;}else{cout<<"ss1 is not a num"<<endl;}if(isNum(ss2)){cout<<"ss2 is a num"<<endl;}else{cout<<"ss2 is not a num"<<endl;}return 0;}bool isNum(string str){    stringstream sin(str);    double d;    char c;    if(!(sin >> d))        return false;    if (sin >> c)        return false;    return true;}

输出结果：

ss1 is not a num

ss2 is a num