Repeat String

Repeat String - Problem

JavaScript Easy

Write code that enhances all strings such that you can call the string.replicate(x) method on any string and it will return repeated string x times.

Note: Try to implement it without using the built-in method string.repeat.

This problem requires extending the String prototype in JavaScript to add a custom method that replicates the string functionality.

Input & Output

Example 1 — Basic Repetition

$ Input: str = "abc", times = 3

› Output: abcabcabc

💡 Note: String 'abc' repeated 3 times gives 'abcabcabc'

Example 2 — Single Character

$ Input: str = "x", times = 5

› Output: xxxxx

💡 Note: Single character 'x' repeated 5 times gives 'xxxxx'

Example 3 — Zero Repetitions

$ Input: str = "hello", times = 0

› Output:

💡 Note: Any string repeated 0 times gives empty string

Constraints

1 ≤ str.length ≤ 1000
0 ≤ times ≤ 100

Visualization

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Asked in

G Google 15 M Microsoft 12

The key insight is to replicate a string without using built-in repeat methods. Best approach uses simple concatenation in a loop or clever array join technique. Time: O(n×x), Space: O(n×x)

Common Approaches

Approach	Time	Space	Notes
✓ Array Join Method	O(n × x)	O(n × x)	Use array of repeated elements and join them into a single string
Character by Character Concatenation	O(n × x)	O(n × x)	Concatenate each character of the original string x times using nested loops
String Concatenation per Iteration	O(n × x)	O(n × x)	Concatenate the entire string x times using a single loop

Array Join Method — Algorithm Steps

Create array of size (times + 1) filled with empty strings
Use join() with original string as separator
Return the joined result

Visualization

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Step-by-Step Walkthrough

Create Array

Make array ["", "", "", ""] of size times+1

Join Operation

Join array elements using 'abc' as separator

Result

Get 'abcabcabc' from join operation

Code -

solution.c — C

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

char* solution(char* str, int times) {
    if (times <= 0) {
        char* empty = malloc(1);
        empty[0] = '\0';
        return empty;
    }
    
    int len = strlen(str);
    char* result = malloc(len * times + 1);
    result[0] = '\0';
    
    // C doesn't have join, use loop concatenation
    for (int i = 0; i < times; i++) {
        strcat(result, str);
    }
    return result;
}

int main() {
    char str[1000];
    int times;
    fgets(str, sizeof(str), stdin);
    str[strcspn(str, "\n")] = 0;
    scanf("%d", &times);
    
    char* result = solution(str, times);
    printf("%s\n", result);
    free(result);
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(n × x)

Join operation processes n×x characters total

✓ Linear Growth

Space Complexity

O(n × x)

Result string and temporary array both use O(n×x) space

⚡ Linearithmic Space

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Input & Output

Constraints

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Related Problems

Common Approaches

Array Join Method — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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