十六进制转换为十进制

函数htoi（s[]）把由十六进制数字组成的字符串（包含可选的前缀0x或0X）转换为与之等价的等价的十进制数。字符串中允许包含的数字包括：0~9，a~f以及A~F。

#define _CRT_SECURE_NO_WARNINGS #include<stdio.h>#define YES 1#define NO 0int htoi(char s[]){int hexdigit, i, inhex, n;i = 0;if (s[i] == '0'){i++;if (s[i] == 'x' || s[i] == 'X')i++;}n = 0;inhex = YES;for (;inhex == YES;i++){if (s[i] >= '0'&&s[i] <= '9')hexdigit = s[i] - '0';else if (s[i] >= 'a'&&s[i] <= 'f')hexdigit = s[i] - 'a'+10;else if (s[i] >= 'A'&&s[i] <= 'F')hexdigit = s[i] - 'A' + 10;elseinhex = NO;if(inhex==YES)n = n * 16 + hexdigit;}return n;}void main(){char str[20];scanf("%s", str);printf("\n%d", htoi(str));system("pause");}