C Exercises: Check if a given string can be interpreted as a decimal number

C Programming Mathematics: Exercise-6 with Solution

Write a C program to check if a given string can be interpreted as a decimal number.

Example:
Input:
str_num1[ ] ="1234"
str_num2[ ]=" 0.1 "
str_num3[ ]=" -90e3 "
str_num4[ ]=" 99e2.5 "
Output:
Is the above string is a number? 1
Is the above string is a number? 1
Is the above string is a number? 1
Is the above string is a number? 0

Sample Solution:

C Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>

bool is_Number(char* str1) {
    int n, m;
    
    // skip leading spaces
    while (*str1 == ' ') str1 ++;
    
    n = m = 0;
    
    // skip the sign of the number
    if (*str1 == '+' || *str1 == '-') str1 ++;
    
    while (*str1 >= '0' && *str1 <= '9') {
        n ++;
        str1 ++;
    }
    
    if (*str1 == '.') {
        str1 ++;
        while (*str1 >= '0' && *str1 <= '9') {
            m ++;
            str1 ++;
        }
        if (!n && !m) return false;
    } else if (!n) {
        return false;
    }
    
    if (*str1 == 'e' || *str1 == 'E') {
        str1 ++;
        if (*str1 == '+' || *str1 == '-') str1 ++;
        n = 0;
        while (*str1 >= '0' && *str1 <= '9') {
            n ++;
            str1 ++;
        }
        if (!n) return false;
    }
    
    while (*str1 == ' ') str1 ++;
    
    return *str1 == 0 ? true : false;
}

int main(void)
{	
   char str_num1[ ] ="1234";
    printf("\nstr_num = %s", str_num1);
    printf("\nIs the above string is a number? %d ",is_Number(str_num1));
    char str_num2[ ]=" 0.1 ";
    printf("\n\nstr_num = %s", str_num2);
    printf("\nIs the above string is a number? %d ",is_Number(str_num2));
    char str_num3[ ]=" -90e3   ";
    printf("\n\nstr_num = %s", str_num3);
    printf("\nIs the above string is a number? %d ",is_Number(str_num3));
    char str_num4[ ]=" 99e2.5 ";
    printf("\n\nstr_num = %s", str_num4);
    printf("\nIs the above string is a number? %d ",is_Number(str_num4));
      return 0;
}

Sample Output:

str_num = 1234
Is the above string is a number? 1 

str_num =  0.1 
Is the above string is a number? 1 

str_num =  -90e3   
Is the above string is a number? 1 

str_num =  99e2.5 
Is the above string is a number? 0 

Flowchart:

C Programming Code Editor:

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