atoi()函数的功能:将字符串转换成整型数;atoi()会扫描参数nptr字符串,跳过前面的空格字符,直到遇上数字或正负号才开始做转换,而再遇到非数字或字符串时(‘\0‘)才结束转化,并将结果返回(返回转换后的整型数)。
atoi()函数实现的代码:
-
- int my_atoi(char* pstr)
- {
- int Ret_Integer = 0;
- int Integer_sign = 1;
-
-
- if(pstr == NULL)
- {
- printf("Pointer is NULL\n");
- return 0;
- }
-
-
- while(isspace(*pstr) == 0)
- {
- pstr++;
- }
-
-
- if(*pstr == ‘-‘)
- {
- Integer_sign = -1;
- }
- if(*pstr == ‘-‘ || *pstr == ‘+‘)
- {
- pstr++;
- }
-
-
- while(*pstr >= ‘0‘ && *pstr <= ‘9‘)
- {
- Ret_Integer = Ret_Integer * 10 + *pstr - ‘0‘;
- pstr++;
- }
- Ret_Integer = Integer_sign * Ret_Integer;
-
- return Ret_Integer;
- }
现在贴出运行my_atoi()的结果,定义的主函数为:int main ()
- int main()
- {
- char a[] = "-100";
- char b[] = "456";
- int c = 0;
-
- int my_atoi(char*);
-
- c = atoi(a) + atoi(b);
-
- printf("atoi(a)=%d\n",atoi(a));
- printf("atoi(b)=%d\n",atoi(b));
- printf("c = %d\n",c);
-
- return 0;
- }
atoi()函数的实现
原文:http://www.cnblogs.com/ranjiewen/p/5335459.html