The "C-language" numeric string is converted to the corresponding number of this string.

(1) The int ascii_to_integer (char *str) function is implemented.

Requirement: This string argument must contain one or more numbers, and the function should convert the numbers to integers and return the integer. If the string argument contains any non-numeric characters, the function returns zero. Don't worry about arithmetic overflow.

tip: Every number you find, multiply the current value by 10 and add the value to the value represented by the new number.

Directly on the code:

#include <stdio.h> #include <assert.h>intAscii_to_integer (Char*Str){intn =0;assert(Str); while(*Str!=' + ')    { while(*Str>=' 0 '&& *Str<=' 9 ')//Determine if the string is all numeric{N. = nTen+ (*Str-' 0 ');Str++; }returnN }return 0;}intMain () {CharA[] ="12345"; printf"%d\n", Ascii_to_integer (a));return 0;}

Explain:

The character pointer subtracts ' 0 ' (corresponding to an ASCII value of 48), converting its corresponding ASCII value to an integer type. The first loop *str points to the character ' 1 ', its corresponding ASCII code value is 49, and ' 0 ' corresponds to the ASCII value 48, so the use of "*str-' 0 '" is to convert the character ' 1 ' to the number 1, and so on.
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(2) The Double my_atof (char *str) function is implemented.

Requirement: converts a numeric string to a number corresponding to this string (including positive floating-point numbers, negative floating-point numbers).

For example: "12.34" returns 12.34; "12.34" returns-12.34

#include <stdio.h>#include <assert.h>DoubleMy_atof (Char*Str){Doublen =0.0;DoubleTMP =10.0;intFlag =0; AssertStr);if(*Str=='-') {flag =1;Str++; } while(*Str>=' 0 '&& *Str<=' 9 ') {n = *Ten+ (*Str-' 0 ');Str++; }if(*Str='. ')      {Str++; while(*Str>=' 0 '&& *Str<=' 9 ') {n = n + (*Str-' 0 ')/tmp;; TMP = TMP *Ten;Str++; }      }if(Flag = =1) {n = ñ; }returnn;}intMain () {CharA[] ="12.345678";CharB[] =" -12.345678"; printf"%f\n%f\n", My_atof (a), my_atof (b));return 0;}

Direct:

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(3) The int my_atoi (char *str) function is implemented.

Requirement: converts a numeric string to a number corresponding to the string (including positive integers, negative integers).

For example: "12" returns 12, "123" returns-123;

#include <stdio.h> #include <assert.h>intMy_atoi (Char*Str){intn =0;intFlag =0;assert(Str);if(*Str=='-') {flag =1;Str++; } while(*Str>=' 0 '&& *Str<=' 9 ') {n = *Ten+ (*Str-' 0 ');Str++; }if(Flag = =1) {n = ñ; }returnn;}intMain () {CharA[] =" A";CharB[] =" -123"; printf"%d\n%d\n", My_atoi (a), My_atoi (b));return 0;}

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The implementation of the above three functions is very similar, just one, the others.

The "C-language" numeric string is converted to the corresponding number of this string.