C + + implements a hexadecimal string conversion to a decimal integer method _c language

This article describes how C + + implements a hexadecimal string conversion to a decimal integer. Share to everyone for your reference. The implementation method is as follows:

 * * Converts a string of hexadecimal digits (including an optional prefix of 0x or 0X) to an integral value equivalent to it/* #include <stdio.h> #include <math.h
 >/* Converts characters in hexadecimal to the corresponding integer */int hexchtoi (char hexch) {char phexch[] = "ABCDEF";
 Char qhexch[] = "abcdef";
 int i; for (i=0;i<6;i++) {if (Hexch = = Phexch[i]) | |
   (Hexch = = Qhexch[i])
 Break
 printf ("i=%d", I);
if (I >= 6) {return 0;/* non-hexadecimal character/} return 10+i;
 int Htoi (char s[]) {int n=0;//* has n-bit/int valu=1;/* valid/int i=0,j;
 int answer=0; /* Validity Check/if ((s[0] = = ' 0 ') && ((s[1] = = ' x ') | | (s[1] = = ' X '))
 {i = 2;
    while ((s[i)!= ' \ n ')) {if (S[i] < ' 0 ') && (S[i] > ' 9 ')) {if (Hexchtoi (s[i)) = = 0) {valu=0;
   Break
  }} n++;
 i++;
  } if (Valu!= 0) {for (j=0;j<n;j++) {answer = = (int) POW (16,j) * Hexchtoi (s[i-j-1)));
 } else Answer =-1;
return answer;
 Main () {char *n[] = {"0x7ff0", "0x2341"};
 printf ("%s is%d\n", N[0],htoi (N[0]));
printf ("%s is%d\n", n[0],123); }

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