Find the Key of the Numbers - Practice Coding Problems

Find the Key of the Numbers - Problem

Math Easy

You are given three positive integers num1, num2, and num3.

The key of num1, num2, and num3 is defined as a four-digit number such that:

Initially, if any number has less than four digits, it is padded with leading zeros.
The ith digit (1 <= i <= 4) of the key is generated by taking the smallest digit among the ith digits of num1, num2, and num3.

Return the key of the three numbers without leading zeros (if any).

Input & Output

Example 1 — Basic Case

$ Input: num1 = 1, num2 = 22, num3 = 333

› Output: 21

💡 Note: Pad to 4 digits: 0001, 0022, 0333. Position-wise minimums: 0,0,2,1 → Key = 0021 → 21

Example 2 — All Same Length

$ Input: num1 = 1234, num2 = 5678, num3 = 9012

› Output: 1012

💡 Note: Already 4 digits. Position-wise minimums: min(1,5,9)=1, min(2,6,0)=0, min(3,7,1)=1, min(4,8,2)=2 → 1012

Example 3 — Leading Zeros Result

$ Input: num1 = 987, num2 = 123, num3 = 456

› Output: 123

💡 Note: Pad to 4 digits: 0987, 0123, 0456. Position-wise minimums: 0,1,2,3 → Key = 0123 → 123

Constraints

1 ≤ num1, num2, num3 ≤ 9999
All three numbers are positive integers

Visualization

Tap to expand

Understanding the Visualization

Input

Three positive integers of varying lengths

Process

Pad to 4 digits and find minimum at each position

Output

Key without leading zeros

Key Takeaway

🎯 Key Insight: Pad all numbers to same length, then compare digits position by position to build the key

Asked in

G Google 15 a Amazon 12

The key insight is to pad all numbers to 4 digits and compare position by position. Best approach is string conversion for simplicity. Time: O(1), Space: O(1)

Common Approaches

Approach	Time	Space	Notes
✓ String Conversion Approach	O(1)	O(1)	Convert numbers to padded strings and compare digits position by position
Mathematical Digit Extraction	O(1)	O(1)	Use arithmetic operations to extract digits without string conversion

String Conversion Approach — Algorithm Steps

Step 1: Convert each number to string and pad with zeros to length 4
Step 2: For each position 0-3, find minimum digit among the three numbers
Step 3: Build result string and convert to integer to remove leading zeros

Visualization

Tap to expand

Step-by-Step Walkthrough

Pad Numbers

Convert to 4-digit strings with leading zeros

Compare Digits

Find minimum digit at each position

Build Key

Combine minimum digits and remove leading zeros

Code -

solution.c — C

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

int solution(int num1, int num2, int num3) {
    // Pad each number to 4 digits
    char s1[5], s2[5], s3[5];
    sprintf(s1, "%04d", num1);
    sprintf(s2, "%04d", num2);
    sprintf(s3, "%04d", num3);
    
    // Build key by finding minimum digit at each position
    char key[5] = {0};
    for (int i = 0; i < 4; i++) {
        char minDigit = s1[i];
        if (s2[i] < minDigit) minDigit = s2[i];
        if (s3[i] < minDigit) minDigit = s3[i];
        key[i] = minDigit;
    }
    
    // Convert to int to remove leading zeros
    return atoi(key);
}

int main() {
    int num1, num2, num3;
    scanf("%d", &num1);
    scanf("%d", &num2);
    scanf("%d", &num3);
    
    int result = solution(num1, num2, num3);
    printf("%d\n", result);
    
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(1)

Fixed 4 iterations regardless of input size

✓ Linear Growth

Space Complexity

O(1)

Only storing fixed-size strings and variables

✓ Linear Space

8.5K Views

Medium Frequency

~8 min Avg. Time

350 Likes

Ln 1, Col 1

Smart Actions

💡 Explanation

AI Ready

💡 Suggestion Tab to accept Esc to dismiss

// Output will appear here after running code

Code Editor Closed

Click the red button to reopen

Input & Output

Constraints

Visualization

Related Problems

Common Approaches

String Conversion Approach — Algorithm Steps

Visualization

Code -

Time & Space Complexity

Select Compiler