CODEWITHSUNDEEP
c
h.kol
h.kol

Reputation: 65

Determining if *char < INT_MAX

I got this code:

char a[151];
scanf ("%150s", a);

In a could be a number and if so, I need to determine, if a < INT_MAX. I don't know, how to do that, because in each index of a char could be a number, it means 150-digit number which could cause overflow if I store a value into some int or anything else. Any suggestions?

Upvotes: 2

Views: 123

Answers (2)

chux
chux

Reputation: 153640

Call strtol() and test errno.

If the correct value is outside the range of representable values, LONG_MIN, LONG_MAX, ... the value of the macro ERANGE is stored in errno. C11dr §7.22.1.4 8

char a[151];
scanf ("%150s", a);
char *endptr;
errno = 0;
long num = strtol(a, &endptr, 10);
if (errno == ERANGE) Overflow();  // outside `long` range
if (num > INT_MAX) Overflow();    // greater than `INT_MAX`

Upvotes: 2

cm161
cm161

Reputation: 510

One way to solve: 

1. INT_MAX = 2147483647 --> contains 10 digits  
2. len = strlen(a);  
3. if (len > 10)   
   a. true --> then a > INT_MAX --> print answer and return  
   b. false, go to step 4  
4. if (len < 10)  
   a. true --> then a < INT_MAX --> print answer and return  
   b. false, go to step 5  
5. (len == 10) case  
6. if (a[9]-'0' > 2) // 10th digit is > 2  
   a. true --> then a > INT_MAX --> print answer and return  
   b. false, go to step 7  
7. int num = atoi(a);  
9. Compare num and INT_MAX and print answer and return

[NOTE: Negative numbers not considered here]

Upvotes: 0

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