string test; test="3527523"; int a=test[3]; std::cout<<a<<std::endl; I was expecting output to be number 7, but I got 55 instead. I have searched through different posts, they all used this method without any problems.. I just don't know where the problem is in my case. Thank you for your help!
test[3] returns char, which you're converting to an integer, so it returns the ASCII value of the character. 3 in ASCII is 55.
Try using char instead as the type of a:
char a = test[3]; std::cout << a; // 3 If you wanted the result to be an integer, subtract the character from '0':
std::string test = "3527523"; int a = test[3] - '0'; std::cout << a; // 3 
'0', '1', '2', '3', '4'... are 48, 49, 50, 51... so when you subtract 51 ('3') from 48 ('0') you get 3. Works for all ASCII digits.
'0' is a character literal and has the ASCII value of 48. When arithmetic is applied to at least one operand of type char, integral promotion is applied. That means '0' is converted to 48. The values of the characters from '0' to '9' are 48 to 53 (do you get it now) :)?'1' to an integer. '1' has the ASCII value 49. Subtracting from '0' (48) gives the integer 1 (49 - 48 == 0).You get the char '7' by the brackets, which has the ASCII code 55 (48+7).
Problem is that you assign test[3] to a variable of type int, thus causing the actual character code (55) to be printed instead of the represented character ('7'). Replace int with char or static_cast before printing.
You don't "cast", you "convert".
You can use sscanf(), atoi() among other functions to convert the value of a string:
int iret = sscanf (test, "%d", &a);
The value of test[3] is the ASCII character '7', which is actually the integer "55".
PS: The beauty of "sscanf()" is that you can easily detect if a parse error occurred by checking for "iret != 1".
Use atoi:
int atoi (const char * str); //Convert string to integer
For example:
string test; test="3527523"; const char c = test[3]; int a=atoi(&c); std::cout<<a<<std::endl; 
int a = test[3]try this:int a = test[3] - '0'. That should print7.