<<Variable Sized Arrays>> _HakerRank_C++_Introdu

#include <cmath>#include <cstdio>#include <vector>#include <iostream>#include <algorithm>using namespace std;int main() {/* Enter your code here. Read input from STDIN. Print output to STDOUT */          int vecrow , querys ;    cin >> vecrow >> querys;        vector<vector<int>> vec ;    vec.resize(vecrow);    for(int i = 0 ; i < vecrow ; i++)    {        int veccolumn, memnum;        cin >> veccolumn ;        vec[i].resize(veccolumn);                for(int j = 0; j < veccolumn ; j++)        {            cin >> memnum ;            vec[i][j] =  memnum ;        }    }        int row, colum ;            for(int i = 0 ; i < querys ; i++)    {        cin >> row >> colum ;        cout << vec[row][colum] << endl ;    }         return 0;}

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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 Kᵢ 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.

Click here to know more about how to create variable sized arrays in C++.

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
．1 <= n <= 10^5
．1 <= q <= 10^5
．1 <= k <= 3 * 10^5
．n <= Σk <= 3 * 10^5
．0 <= i < n
．0 <= j < k
．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[0] = [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[1] = [1, 2, 8, 9, 3]. We must print the value at index j = 3 of this array which, as you can see, is 9.