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Merge k sorted arrays of different sizes in C++
Suppose we have different k sorted arrays. We have to merge these arrays and display the sorted result.
So, if the input is like k = 3 and arrays are {2, 4},{3, 5, 7},{1, 10, 11, 12} , then the output will be 1 2 3 4 5 7 10 11 12
To solve this, we will follow these steps −
- define one type of pair with first element is an integer and second element is another pair of integers, name it as ppi.
- Define an array op
- define one priority queue q
- for initialize i := 0, when i < size of arr, update (increase i by 1), do −
- insert (arr[i, 0], {i, 0} )into q
- while q is not empty, do −
- current_element := top element of q
- delete element from q
- i := second element from current_element
- j := third element from current_element
- insert first element of current_element at the end of op
- if j + 1 < size of arr[i], then &minus
- insert (arr[i, j+1], {i, j+1} )into q
- return op
Example
Let us see the following implementation to get better understanding −
#include <bits/stdc++.h>
using namespace std;
#define ppi pair<int,pair<int,int>>
vector<int> merge(vector<vector<int> > arr){
vector<int> op;
priority_queue<ppi, vector<ppi>, greater<ppi> > queue;
for (int i = 0; i < arr.size(); i++)
queue.push({ arr[i][0], { i, 0 } });
while (queue.empty() == false) {
ppi current_element = queue.top();
queue.pop();
int i = current_element.second.first;
int j = current_element.second.second;
op.push_back(current_element.first);
if (j + 1 < arr[i].size())
queue.push({ arr[i][j + 1], { i, j + 1 } });
}
return op;
}
int main(){
vector<vector<int> > arr{ { 2,4}, { 3,5,7 }, { 1, 10, 11, 12 } };
vector<int> output = merge(arr);
for(int i = 0; i<output.size(); i++)
cout << output[i] << " ";
}Input
{{ 2,4}, { 3,5,7 }, { 1, 10, 11, 12 }}Output
1 2 3 4 5 7 10 11 12
Updated on: 27-Aug-2020
444 Views
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