C PROGRAMMING PROGRAM • LOOPS & NUMBER PROBLEMS

Find GCD Using Euclid's Loop

Learn how to find gcd using euclid's loop using a clear C program.

IntermediateEuclid's algorithmwhile loopModulus

PROBLEM UNDERSTANDING

Input and expected output

Sample input

84 30

Sample output

GCD = 6

COMPLETE C PROGRAM

Complete C implementation

#include <stdio.h>

int main(void)
{
    int first, second;

    printf("Enter two positive integers: ");
    scanf("%d %d", &first, &second);
    if (first < 0) first = -first;
    if (second < 0) second = -second;
    while (second != 0) {
        int remainder = first % second;
        first = second;
        second = remainder;
    }
    printf("GCD = %d\n", first);
    return 0;
}

CURRENT STEP

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SELECTED LINE

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EXPECTED OUTPUT FOR THE SAMPLE

GCD = 6

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Replace the pair with divisor and remainder until the remainder becomes zero.
Display the computed result.

Replace the pair with divisor and remainder until the remainder becomes zero.

EFFICIENCY

Time and space complexity

Time complexity

O(log min(a,b))

Auxiliary space

O(1)

DEBUGGING CHECKLIST

Common mistakes

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Use the correct format specifier for every variable.

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Initialize variables before using their values.

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Check braces, semicolons and input order carefully.

Try it yourself

Practice: Run the program with the sample input, predict its output, and then test one boundary case of your own.