A sparse vector is a vector that has a large number of zeros so it takes unwanted space to store this zeroes.
The task is to store a given sparse vector efficiently without storing the zeros.
Examples:
Input: vector = { 2, 0, 0, 0, 0,
3, 0, 4, 0, 0,
0, 1, 5, 0, 0,
0, 0, 0, 0, 0,
0, 0, 4, 0, 0,
0, 2, 0, 0, 0,
0, 0, 0, 3, 0,
0, 0, 1, 0, 0,
0, 0, 5 }
Output: {2, 3, 4, 1, 5,
4, 2, 3, 1, 5}
Approach:
To store the sparse vector efficiently, a vector of pairs can be used. The First element of pair will be the index of spare vector element(which is non-zero) and the second element will be the actual element.
Below is the implementation of the above approach:
C++
// C++ program to store sparse vectors // with the help of vector of pair #include <bits/stdc++.h> using namespace std; // Store the sparse vector // as a vector of pairs vector<pair<int, int> > convertSparseVector(vector<int> v) { vector<pair<int, int> > res; for (int i = 0; i < v.size(); i++) { if (v[i] != 0) { res.push_back(make_pair(i, v[i])); } } return res; } // Print the vector of pairs void print(vector<pair<int, int> > res) { for (auto x : res) { cout << "index: " << x.first << " -> value: " << x.second << endl; } } // Driver function int main() { // Get the sparse vector vector<int> v{ 2, 0, 0, 0, 0, 3, 0, 4, 0, 0, 0, 1, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 1, 0, 0, 0, 0, 5 }; // Get the stored vector of pairs vector<pair<int, int> > res = convertSparseVector(v); // Print the vector of pairs print(res); return 0; } |
Python 3
# Python3 program to store sparse vectors # with the help of vector of pair # Store the sparse vector # as a vector of pairs def convertSparseVector(v): res = [] for i in range(len(v)): if (v[i] != 0): res.append([i, v[i]]) return res # Print the vector of pairs def printf(res): for x in res: print("index:", x[0], " -> value:", x[1]) # Driver Code if __name__ == '__main__': # Get the sparse vector v = [2, 0, 0, 0, 0, 3, 0, 4, 0, 0, 0, 1, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 1, 0, 0, 0, 0, 5] # Get the stored vector of pairs res = convertSparseVector(v) # Print the vector of pairs printf(res) # This code is contributed by Surendra_Gangwar |
index: 0 -> value: 2 index: 5 -> value: 3 index: 7 -> value: 4 index: 11 -> value: 1 index: 12 -> value: 5 index: 22 -> value: 4 index: 26 -> value: 2 index: 33 -> value: 3 index: 37 -> value: 1 index: 42 -> value: 5
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Improved By : SURENDRA_GANGWAR
