# Convert to Strictly increasing array with minimum changes

Given an array of n integers. Write a program to find minimum number of changes in array so that array is strictly increasing. In strictly increasing array A[i] < A[i+1] for 0 <= i < n

Examples:

```Input : arr[] = { 1, 2, 6, 5, 4}
Output : 2
We can a[2] to any value between 2 and 5
and a[4] to any value greater then 5.

Input : arr[] = { 1, 2, 3, 5, 7, 11 }
Output : 0
```

## Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

The problem is variation of Longest Increasing Subsequence. The numbers which are already a part of LIS need not to be changed. So minimum elements to change is difference of size of array and number of elements in LIS.

## C++

```// CPP program to find min elements to
// change so array is strictly increasing
#include <bits/stdc++.h>
using namespace std;

// To find min elements to remove from array
// to make it strictly increasing
int minRemove(int arr[], int n)
{
int LCS[n], len = 0;

// Mark all elements of LCS as 1
for (int i = 0; i < n; i++)
LCS[i] = 1;

// Find LCS of array
for (int i = 1; i < n; i++) {
for (int j = 0; j < i; j++) {
if (arr[i] > arr[j])
LCS[i] = max(LCS[i], LCS[j] + 1);
}
len = max(len, LCS[i]);
}

// Return min changes for array
// to strictly increasing
return n - len;
}

// Driver program to test minRemove()
int main()
{
int arr[] = { 1, 2, 6, 5, 4 };
int n = sizeof(arr) / sizeof(arr[0]);

cout << minRemove(arr, n);

return 0;
}
```

## Java

```// Java program to find min elements to
// change so array is strictly increasing
public class Main {

// To find min elements to remove from array
// to make it strictly increasing
static int minRemove(int arr[], int n)
{
int LCS[] = new int[n];
int len = 0;

// Mark all elements of LCS as 1
for (int i = 0; i < n; i++)
LCS[i] = 1;

// Find LCS of array
for (int i = 1; i < n; i++) {
for (int j = 0; j < i; j++) {
if (arr[i] > arr[j])
LCS[i] = Math.max(LCS[i],
LCS[j] + 1);
}
len = Math.max(len, LCS[i]);
}

// Return min changes for array
// to strictly increasing
return n - len;
}

// Driver program to test minRemove()
public static void main(String[] args)
{
int arr[] = { 1, 2, 6, 5, 4 };
int n = arr.length;

System.out.println(minRemove(arr, n));
}
}
```

Output:

```2
```

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