C++

1/**
2 * Runtime: 8 ms, faster than 94.80% 
3 * Memory Usage: 15.4 MB, less than 63.23%
4 */
5class Solution {
6public:
7    string restoreString(string s, vector<int>& indices) {
8        string result (indices.size(), 'a');
9        int j=0;
10        for(int i : indices) 
11        {
12            result[i] = s[j++];
13        }
14        
15        return result;
16    }
17};

JavaScript

1/**
2 * Runtime: 88 ms, faster than 73.88%
3 * Memory Usage: 39.2 MB, less than 79.04%
4 */
5var restoreString = function(s, indices) {
6    let result = new Array(indices.length);
7    let j = 0;
8    indices.forEach(i => {
9        result[i] = s[j];
10        j+=1
11    })
12    
13    return result.join('');
14};

Ruby

1# Runtime: 68 ms, faster than 41.18%
2# Memory Usage: 210.4 MB, less than 36.97%
3def restore_string(s, indices)
4    result = 'a' * indices.size
5    j = 0
6    indices.each do |i|
7        result[i] = s[j] 
8        j += 1
9    end
10    
11    return result
12end