Array Transformation in C++

Suppose there is an initial array arr, consider every day we produce a new array using the array of the previous day. On the i-th day, we will perform the following operations on the array of day i-1 to produce the array of the day i. The conditions are as follows −

• If an element is smaller than both its left and its right adjacent values, then this element is incremented.

• If an element is bigger than both its left and its right adjacent values, then this element is decremented.

• The first and last elements will remain same.

After some days, the array does not change anymore. find that final array. So if the initial array is [6,2,3,4] then the output is [6,3,3,4]. On the first day, the array will be changed from [6,2,3,4] to [6,3,3,4], then no more operation will be performed.

To solve this, we will follow these steps −

• if array size is 2 or less than 2, then return array
• set flag := true
• while flag is true −
  • set flag := false
  • create one empty array called temp, and insert arr[0] into temp
  • for i in range 1 to array size – 1
    • if arr[i] < arr[i - 1] and arr[i] < arr[i + 1], then insert arr[i] + 1 into temp, and set flag as true
    • otherwise when arr[i] > arr[i - 1] and arr[i] > arr[i + 1], then insert arr[i] – 1 into the temp, and set flag := true
    • otherwise insert arr[i] into temp
  • insert last element of arr into temp
  • arr := temp
• return arr

Example(C++)

Let us see the following implementation to get a better understanding −

 Live Demo

#include <bits/stdc++.h>
using namespace std;
#define push push_back
void print_vector(vector<auto> v){
   cout << "[";
   for(int i = 0; i<v.size(); i++){
      cout << v[i] << ", ";
   }
   cout << "]"<<endl;
}
class Solution {
public:
   vector<int> transformArray(vector<int>& arr) {
      if(arr.size()<=2)return arr;
      bool flag = true;
      while(flag){
         flag = false;
         vector <int> temp;
         temp.push_back(arr[0]);
         for(int i = 1; i < arr.size()-1; i++){
            if(arr[i]< arr[i-1] && arr[i]<arr[i+1]){
               temp.push(arr[i]+1);
               flag = true;
            }
            else if(arr[i]> arr[i-1] && arr[i]>arr[i+1]){
               flag = true;
               temp.push(arr[i]-1);
            }
            else temp.push(arr[i]);
         }
         temp.push_back(arr[arr.size()-1]);
         arr = temp;
      }
      return arr;
   }
};
main(){
   Solution ob;
   vector<int> v = {1,6,3,4,3,5};
   print_vector(ob.transformArray(v));
}

Input

[1,6,3,4,3,5]

Output

[1,4,4,4,4,5]