Variable Sized Arrays C++ HackerRank Solution
Consider an n-element array, a, where each index i in the array contains a reference to an array of ki integers (where the value of varies from array to array). See the Explanation section below for a diagram.
Given a, you must answer q queries. Each query is in the format i j, where i denotes an index in array a and j denotes an index in the array located at a[i]. For each query, find and print the value of element j in the array at location a[i] on a new line.
Input Format
The first line contains two space-separated integers denoting the respective values of n (the number of variable-length arrays) and q (the number of queries).
Each line i of the n subsequent lines contains a space-separated sequence in the format k a[i]0 a[i]1 … a[i]k-1 describing the k-element array located at a[i].
Each of the q subsequent lines contains two space-separated integers describing the respective values of i (an index in array a) and j (an index in the array referenced by a[i]) for a query.
Constraints
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1 <= n <= 10^5
-
1 <= q <= 10^5
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1 <= k <= 3 . 10^5
-
n <= Σk <= 3 . 10^5
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0 <= i < n
-
0 <= j < k
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All indices in this challenge are zero-based.
-
All the given numbers are non negative and are not greater than 10^6.
Output Format
For each pair of i and j values (i.e., for each query), print a single integer that denotes the element located at index j of the array referenced by a[i]. There should be a total of q lines of output.
Sample Input
2 2
3 1 5 4
5 1 2 8 9 3
0 1
1 3
Sample Output
5
9
Explanation
The diagram below depicts our assembled Sample Input:
We perform the following q=2 queries:
Find the array located at index i = 0 , which corresponds to a[i] = [1,5,4]. We must print the value at index j=1 of this array which, as you can see, is 5.
Find the array located at index i=1 , which corresponds to a[i] = [1,2,8,9,3]. We must print the value at index j=3 of this array which, as you can see, is 9.
Solution
#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;
int main() {
int n, q;
cin >> n >> q;
vector<std::vector<int>> arr(n);
for (int i = 0; i < n; i++) {
int size;
cin >> size;
arr[i].resize(size);
for (int j = 0; j < size; j++) {
cin >> arr[i][j];
}
}
for (int k = 0; k < q; k++) {
int i, j;
cin >> i >> j;
cout << arr[i][j] << endl;
}
return 0;
}
