面试题54：表示数值的字符串

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/*  * Question Description: * (Question 12 in <Coding Intervies>) How do you check whether a string stands for a number or not?  * Numbers include positive and negative integers and floats. For example, strings “+100.”, “5e2”, “-.123”, “3.1416”, and “-1E-16”  * stand for numbers, but “12e”, “1a3.14”, “1.2.3”, “+-5”, and “12e+5.4” do not. */#include <stdio.h>void scanDigits(char** string);bool isExponential(char** string);bool isNumeric(char* string){    if(string == NULL)        return false;    if(*string == '+' || *string == '-')        ++string;    if(*string == '\0')        return false;    bool numeric = true;    scanDigits(&string);    if(*string != '\0')    {        // for floats        if(*string == '.')        {            ++string;            scanDigits(&string);                        if(*string == 'e' || *string == 'E')                numeric = isExponential(&string);        }        // for integers        else if(*string == 'e' || *string == 'E')            numeric = isExponential(&string);        else            numeric = false;    }    return numeric && *string == '\0';}void scanDigits(char** string){    while(**string != '\0' && **string >= '0' && **string <= '9')        ++(*string);}bool isExponential(char** string){    if(**string != 'e' && **string != 'E')        return false;            ++(*string);    if(**string == '+' || **string == '-')        ++(*string);    if(**string == '\0')        return false;    scanDigits(string);    return (**string == '\0') ? true : false;}// ==================== Test Code ====================void Test(char* testName, char* string, bool expected){    if(testName != NULL)        printf("%s begins: ", testName);    if(isNumeric(string) == expected)        printf("Passed.\n");    else        printf("FAILED.\n");}int main(int argc, char* argv[]){    Test("Test1", "100", true);    Test("Test2", "123.45e+6", true);    Test("Test3", "+500", true);    Test("Test4", "5e2", true);    Test("Test5", "3.1416", true);    Test("Test6", "600.", true);    Test("Test7", "-.123", true);    Test("Test8", "-1E-16", true);    Test("Test9", "1.79769313486232E+308", true);    printf("\n\n");    Test("Test10", "12e", false);    Test("Test11", "1a3.14", false);    Test("Test12", "1+23", false);    Test("Test13", "1.2.3", false);    Test("Test14", "+-5", false);    Test("Test15", "12e+5.4", false);return 0;}
https://github.com/zhedahht/ChineseCodingInterviewAppendix/blob/master/NumericStrings/NumericString.cpp
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