C ++ converts a string to a number.

1 int changestr (char * str)
2 {
3 int len = strlen (str );
4 int sum = 0;
5 float carry = 1.0/10;
6 for (int I = 0; I <len; I ++)
7 {
8 carry * = 10;
9 sum + = (str [len-1-i]-'0') * carry;
10}
11 return sum;
12}
Sum is the carry value before the current BIT.

Str [len-1-i]-'0' represents the ascii code of the character minus the ascii code of 0, and the final number is the expected number.

The current BIT is moved forward every time x 10.

 

* The algorithm is improved, the negative number is supported, and throw exception occurs when a problematic character is encountered.