【C语言】编写函数实现库函数atoi，把字符串转换成整形（考虑数字过大）

//编写函数实现库函数atoi，把字符串转换成整形#include <stdio.h>#include <string.h>#include <assert.h>#include <ctype.h>long long calculate(const char *src, int flag){long long num = 0;while (*src ){if ((*src >= '0') && (*src <= '9'))//判断输⼊入是否为⾮非数组字符{num = num * 10 + (*src - '0');if ((flag == 1 && num>0x7fffffff) ||(flag == -1 && num < (signed int)0x80000000))//考虑数字太⼤大{num = 0;break;}src++;}else{num = 0;break;}}return flag * num;}long long str_to_int(const char *str){long long num = 0;if (str != NULL && *str != '\0'){while (isspace(*str)){str++;}int flag = 1;if (*str == '+')str++;else if (*str == '-'){str++;flag = -1;}if (*str != '\0'){num = calculate(str, flag);}}return num;}int main(){printf("%lld\n", str_to_int(" +2345"));printf("%lld\n", str_to_int(" -2345"));printf("%lld\n", str_to_int("+2345"));printf("%lld\n", str_to_int("-2345"));printf("%lld\n", str_to_int("2345"));printf("%lld\n", str_to_int("-111111111"));printf("%lld\n", str_to_int(""));printf("%lld\n", str_to_int("123ab"));return 0;}