Minimal replacements with 0 to type the array
Given an array A[] of N integers, the duty is to search out the minimal variety of operations to type the array in nondecreasing order, by selecting an integer X and changing all of the occurrences of X within the array with 0.
Examples:
Enter: N = 5, A[] = {2, 2, 1, 1, 3}
Output: 1
Rationalization: We select X = 2 and exchange all of the occurrences of two with 0. Now the array turns into {2, 2, 1, 1, 3} > {0, 0, 1, 1, 3} , which is sorted in rising order.Enter: N = 4, A[] = {2, 4, 1, 2}
Output: 3
Strategy: The issue will be solved simply with the assistance of a Map.
Observations:
There are 2 circumstances that must be thought of :
 Case 1: Similar aspect happens greater than as soon as noncontiguously
 Think about the array : {1,6,3,4,5,3,2}.
 Now, since 3 at index 5 is larger than its subsequent aspect, so we are going to make that 0 (in addition to 3 at index 2).
 The array turns into {1,6,0,4,5,0,2}.
 So, the one solution to type the array can be to make all the weather earlier than the zeroes equal to 0. i.e. the array turns into {0,0,0,0,0,0,2}.
 Case 2: Factor at ith index is larger than the aspect at (i+1)th index :
 Think about the array : {1,2,3,5,4}.
 For the reason that aspect on the third index is larger than the aspect at 4th index, we’ve to make the aspect at third index equal to zero.
 So , the array turns into {1,2,3,0,4}.
 Now, the one solution to type the array can be to make all the weather earlier than the zero equal to 0. i.e. the array turns into {0,0,0,0,4}.
It may be noticed that in the long run Case 2 breaks all the way down to Case 1.
Contemplating the above circumstances, the issue will be solved following the under steps :
 Declare a hash map and add the frequency of every aspect of the array into the map.
 Iterate via the array from the again, i.e. from i=N1 to i=0.
 At every iteration, deal with Circumstances 1 and a couple of as defined above.
 If iteration completes, return 0.
Under is the implementation of this strategy:
C++

Time Complexity: O(N)
Auxiliary Area: O(N)