Shuffle String

Shuffle String - Problem

Array String Easy

You are given a string s and an integer array indices of the same length. The string s will be shuffled such that the character at the ith position moves to indices[i] in the shuffled string.

Return the shuffled string.

Input & Output

Example 1 — Basic Shuffling

$ Input: s = "codeleet", indices = [4,5,6,7,0,2,1,3]

› Output: "leetcode"

💡 Note: Characters are rearranged: s[0]='c' goes to indices[0]=4, s[1]='o' goes to indices[1]=5, etc. Result: "leetcode"

Example 2 — Short String

$ Input: s = "abc", indices = [0,1,2]

› Output: "abc"

💡 Note: Each character stays in the same position: 'a' at 0, 'b' at 1, 'c' at 2

Example 3 — Complete Reversal

$ Input: s = "aiohn", indices = [3,1,4,2,0]

› Output: "nihao"

💡 Note: s[0]='a' → pos 3, s[1]='i' → pos 1, s[2]='o' → pos 4, s[3]='h' → pos 2, s[4]='n' → pos 0

Constraints

s.length == indices.length
1 ≤ s.length ≤ 100
s contains only lowercase English letters
0 ≤ indices[i] < s.length
All values of indices are unique

Visualization

Tap to expand

Asked in

M Microsoft 15 a Amazon 12 G Google 8

The key insight is that each character has a predetermined destination position. The optimal approach creates a result array and places each character directly at its target position in O(n) time. Best approach: Character by Character Placement - Time: O(n), Space: O(n)

Common Approaches

✓ Character by Character Placement

⏱️ Time: O(n) Space: O(n)

Create a result array and iterate through each character in the original string, placing it at the position specified by the corresponding index in the indices array.

Direct String Building

⏱️ Time: O(n²) Space: O(1)

Use string concatenation or string builder to construct the result directly by processing characters in order of their target positions.

Character by Character Placement — Algorithm Steps

Create result array of same length
For each character, place it at indices[i] position
Convert result array back to string

Visualization

Tap to expand

Step-by-Step Walkthrough

Original String

Each character has a corresponding index

Place Characters

Move each character to its target position

Result

Shuffled string formed

Code -

solution.c — C

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

char* solution(char* s, int* indices, int length) {
    char* result = (char*)malloc((length + 1) * sizeof(char));
    result[length] = '\0';
    
    for (int i = 0; i < length; i++) {
        result[indices[i]] = s[i];
    }
    
    return result;
}

int main() {
    char s[1001];
    fgets(s, sizeof(s), stdin);
    s[strcspn(s, "\n")] = 0;
    
    char line[10001];
    fgets(line, sizeof(line), stdin);
    
    // Parse array
    int indices[1000];
    int length = 0;
    char* token = strtok(line + 1, ",]");
    while (token != NULL) {
        indices[length++] = atoi(token);
        token = strtok(NULL, ",]");
    }
    
    char* result = solution(s, indices, length);
    printf("%s\n", result);
    
    free(result);
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(n)

Single loop through n characters, each placement is O(1)

✓ Linear Growth

Space Complexity

O(n)

Result array stores n characters

⚡ Linearithmic Space

72.8K Views

Medium Frequency

~8 min Avg. Time

2.1K 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

Character by Character Placement — Algorithm Steps

Visualization

Code -

Time & Space Complexity

Select Compiler