Conversion between a string and the corresponding integer

The C language provides several standard library functions that convert numbers of any type (integer, long, float, and so on) to a string. The following respectively converts the string to the corresponding integer using the My_atoi () function, and converts the integer to a string using the Itoa () function.

atoi Converting a string to an integer number
Itoa converting an integer to a string

1, implement a function int my_atoi (char s[]), you can convert a string to the corresponding integer.

For example: Enter the string "1234" and return the number 1234.

Enter the string "+1234" and return the number 1234.

Enter the string "1234" and return the number-1234.

The code is as follows:

#include <stdio.h> #include <assert.h> #include <ctype.h> #include <stdlib.h>int my_atoi (char * p) {int flag=1,rav=0;assert (p), while (Isspace (*p))//Determine if the pointer is a white-space character {*p++;} if (*p== '-') {Flag=-1;//flag save symbol Plus/minus}if (*p== '-' | | *p== ' + ')//If the sign bit is moved after {p++;} while (*P)//assigns each bit of the number to Rav, which is equivalent to while (*p!= ') {if (*p>= ' 0 ') && (*p<= ' 9 ')) {rav=rav*10+ (*p-' 0 ');        /*p-' 0 ' is the number}p++ each time it is taken out;}        Return flag*rav;//returns the product of the symbol and number}int main () {char str[10]; Gets (str);//Enter a string printf ("%d\n", My_atoi (str)); system ("pause"); return 0;}

2 . Implement a function itoa (int n,char s[]), convert the number of integer n to the corresponding string, and save to S.

The code is as follows:

#include <stdio.h> #include <stdlib.h>void reverse (char str[],int len)//reverse the entire character array {int  left=0;int right=len-1;while (left<right) {Char temp=str[left];str[left]=str[right];str[right ]=temp;left++;right--;}} Void itoa (int num, char str[]) {    int i=0,j,flag;     flag=num;//flag Save Symbol     if (num<0)//Convert to positive if the number entered is negative       num=-num;    while (num)     {str[i++]=num%10+ ' 0 ';//number in reverse order in character array     num/=10;}     if (flag<0) {str[i++]= '-';///character array stored in symbol}    str[i]= ' + ';     reverse (str,i);} Int main (void) {&NBSP;CHAR&NBSP;STR[20];INT&NBSP;NUM;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;SCANF ("%d", &num); Itoa (NUM,STR);p rintf ("%s\n", str);     system ("Pause");     return 0;}

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Conversion between a string and the corresponding integer