C＋+判断String是否以数字开头

可以使用isdigit()函数来判断一个字符串是否以数字开头，示例代码如下：

#include <iostream>
#include <string>

using namespace std;

bool isStartWithDigit(string str) {
    if (isdigit(str[0])) {
        return true;
    }
    return false;
}

int main() {
    string str1 = "123abc";
    string str2 = "abc123";

    if (isStartWithDigit(str1)) {
        cout << str1 << " starts with digit." << endl;
    } else {
        cout << str1 << " does not start with digit." << endl;
    }

    if (isStartWithDigit(str2)) {
        cout << str2 << " starts with digit." << endl;
    } else {
        cout << str2 << " does not start with digit." << endl;
    }

    return 0;
}

输出结果为：

123abc starts with digit.
abc123 does not start with digit.