【C語言】編寫函數實現庫函數atof

標籤：

//編寫函數實現庫函數atof#include <stdio.h>#include <assert.h>#include <ctype.h>#include <math.h>double calculate(const char *src, int flag){double num = 0.0;int n = 0;int count = 0;while (*src){if ((*src >= '0') && (*src <= '9'))//判斷輸?入是否為?非數組字元{num = num * 10 + (*src - '0');src++;if (n){count++;}}else if (*src == '.'){n = 1;src++;}else{num = 0;break;}}if (n){num = num / powl(10,count);}return flag * num;}double str_to_int(const char *str){double num = 0.0;int flag = 1;if (str != NULL && *str != '\0'){while (isspace(*str)){str++;}if (*str == '+')str++;else if (*str == '-'){str++;flag = -1;} if (*str != '\0'){num = calculate(str, flag);}}return num;}int main(){printf("%f\n", str_to_int(" +23.45"));printf("%f\n", str_to_int(" -2.345"));printf("%f\n", str_to_int("+234.5"));printf("%f\n", str_to_int("-2345.44"));printf("%f\n", str_to_int("2345"));printf("%f\n", str_to_int("-1111.11"));printf("%f\n", str_to_int(""));printf("%f\n", str_to_int("123ab"));return 0;}

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【C語言】編寫函數實現庫函數atof