C PROGRAMMING PROGRAM • DECISION MAKING

Check Whether Three Sides Form a Valid Triangle

Learn how to check whether three sides form a valid triangle using a clear C program.

BeginnerTriangle inequalityLogical ANDValidation

PROBLEM UNDERSTANDING

Input and expected output

Sample input

5 6 7

Sample output

Valid triangle

COMPLETE C PROGRAM

Complete C implementation

#include <stdio.h>

int main(void)
{
    double first, second, third;

    printf("Enter three side lengths: ");
    scanf("%lf %lf %lf", &first, &second, &third);
    if (first > 0 && second > 0 && third > 0 &&
        first + second > third && first + third > second && second + third > first)
        printf("Valid triangle\n");
    else
        printf("Invalid triangle\n");
    return 0;
}

CURRENT STEP

Select Start to walk through the important lines.

SELECTED LINE

No line selected

EXPECTED OUTPUT FOR THE SAMPLE

Valid triangle

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Verify positive lengths and all three triangle inequalities.
Display the computed result.

Verify positive lengths and all three triangle inequalities.

EFFICIENCY

Time and space complexity

Time complexity

O(1)

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.