1.求两个字符串的乘积，结果存到字符串中，例如字符串一中存的“657891”，字符串二中存的“521”，分别将字符串中的字符转换成整型数字，进行计算后，再转换成字符类型存储起来-Find the product of two strings, the result is stored in the string, such as strings saved " 657,891" , string II memory " 521" , respectively convert characters in a string to an integer number calculated, converted to a character type stored