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Program to Find Out Median of an Integer Array in C++
Suppose we have to implement a class named MedianClass which contains the following methods −
add(value) which adds a value to the data structure.
median() finds the median of all the numbers currently present in the data structure.
So, if we add 5, 3, 8 and find median, the output will be 5.0, then if we add 9 and find the median, the output will be 6.5.
To solve this, we will follow these steps −
Define priority queue left and right
Define addNum method, this will take the number as input −
if left is empty or num < top element of left, then,
insert num into left
Otherwise
insert num into right
if size of left < size of right, then,
temp := top element of right
delete item from right
insert temp into left
if size of left − size of right > 1, then,
temp := top element of left
delete item from left
insert temp into right
Define findMedian() method, this will act as follows −
return top of left if size of left > size of right, else (top of left + top of right)/2Let us see the following implementation to get better understanding −
Example
#include <bits/stdc++.h>
using namespace std;
typedef double lli;
class MedianClass {
priority_queue <int> left;
priority_queue <int, vector <int>, greater<int>> right;
public:
void addNum(int num) {
if(left.empty() || num<left.top()){
left.push(num);
}else right.push(num);
if(left.size()<right.size()){
lli temp = right.top();
right.pop();
left.push(temp);
}
if(left.size()−right.size()>1){
lli temp = left.top();
left.pop();
right.push(temp);
}
}
double findMedian() {
return
left.size()>right.size()?left.top():(left.top()+right.top())*0.5;
}
};
main(){
MedianClass ob;
ob.addNum(5);
ob.addNum(3);
ob.addNum(8);
cout << ob.findMedian() << " ";
ob.addNum(9);
cout << ob.findMedian() << endl;
}Input
ob.addNum(5); ob.addNum(3); ob.addNum(8); cout << ob.findMedian() << endl; ob.addNum(9); cout << ob.findMedian() << endl;
Output
5.0 6.5
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