char字符+-‘0’

ASCII编码0是48,1是49,2是50....

-‘0’：char变int

char *p = "123"字符串;(我要计算出1*2*3 = 6)
//p[0] = 49;// '1'
//p[1] = 50;// '2'
//p[2] = 51;// '3'
// '0' = 48;

int int_1 = p[0]-'0'; //相当于49-48 = 1
int int_2 = p[1]-'0'; //相当于50-48 = 2
int int_3 = p[2]-'0'; //相当于51-48 =3

int_1 * int_2 * int_3 = 1*2*3 = 6;

 

+'0'：int变char