Program to check if input numbers are Pythagorean triplets.

right_angled_triangle.c

// Written by Nam Tran Ngoc

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

int main() {
  unsigned int a, b, c;
  printf("Please enter three positive integers as sides of a triangle, separated between spaces: \n");
  scanf("%d %d %d", &a, &b, &c);
  
  // Since a, b, c are unsigned, they can't be negatives, so you only have to check if they exceed the bounds.
  if(a <= 1000 && b <= 1000 && c <= 1000) {
    if(a*a + b*b == c*c || b*b + c*c == a*a || c*c + a*a == b*b) {
      printf("Yes.\n");
    } else {
      printf("No.\n");
    }
  } else {
    printf("The lengths are too great\n");
    // Return 1 to indicate error.
    return 1;
  }
  
  return 0;
}

Alternatively:

if ( (a > 0 && a <= 1000) &&
   ( (b > 0 && b <= 1000) &&
   ( (c > 0 && c <= 1000)) {

    ...
}

Or, better yet:

int is_within_bounds(int x, int lower, int upper) {
  if (x >= lower && x <= upper) {
    return 1;
  } else return 0;
}

...

if (is_within_bounds(a, 0, 1000) && is_within_bounds(b, 0, 1000) && is_within_bounds(c, 0, 1000) {
  ...
}