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The k Strongest Values in an Array in C++
Suppose we have an array of numbers called arr and an integer k. There is a value arr[i] that is said to be stronger than a value arr[j] when |arr[i] - m| > |arr[j] - m| where m is the median of the array. If |arr[i] - m| is same as the |arr[j] - m|, then arr[i] is said to be stronger than arr[j] if arr[i] > arr[j]. So we have to find a list of the strongest k values in the array.
So, if the input is like arr = [1,2,3,4,5], k = 2, then the output will be [5,1], this is because median is 3, and the elements of the array sorted by the strongest are [5,1,4,2,3]. Here the strongest 2 elements are [5, 1]. [1, 5] is also valid. Although |5 - 3| is same as |1 - 3| but 5 is stronger than 1 because 5 > 1.
To solve this, we will follow these steps −
sort the array arr
n := size of arr
m := arr[(n - 1)/2]
Define an array v of pairs
i := 0, j := n - 1
Define an array ret
while k is non-zero, decrease k in each iteration, do −
x1 := |arr[j]- m|
x2 := |arr[i]- m|
if x1 >= x2, then −
insert arr[j] at the end of ret
(decrease j by 1)
Otherwise
insert arr[i] at the end of ret
(increase i by 1)
return ret
Example
Let us see the following implementation to get a better understanding −
#include <bits/stdc++.h>
using namespace std;
void print_vector(vector<int> v){
cout << "[";
for(int i = 0; i<v.size(); i++){
cout << v[i] << ", ";
}
cout << "]"<<endl;
}
class Solution {
public:
int calc(int x, int m){
return abs(x - m);
}
vector<int> getStrongest(vector<int>& arr, int k) {
sort(arr.begin(), arr.end());
int n = arr.size();
int m = arr[(n - 1) / 2];
vector<pair<int, int> > v;
int i = 0;
int j = n - 1;
vector<int> ret;
while (k--) {
int x1 = calc(arr[j], m);
int x2 = calc(arr[i], m);
if (x1 >= x2) {
ret.push_back(arr[j]);
j--;
}
else {
ret.push_back(arr[i]);
i++;
}
}
return ret;
}
};
main(){
Solution ob;
vector<int> v = {1,2,3,4,5};
print_vector(ob.getStrongest(v,2));
}Input
{1,2,3,4,5},2Output
[5, 1, ]
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