Minimum Replacements to Make Every Value Contiguous

Problem Description You are given an integer array arr of length n. In one operation, you may choose two integers x and y, and replace all occurrences of x in the array with y simultaneously. Your goal is to use the minimum number of operations so that in the final array, every distinct value appears in one contiguous segment only. In other words, if a value v appears at positions l and r in the final array, then every position between l and r must also contain v. Adjacent duplicate values do not affect the answer. For example, [1,1,2,1] can be compressed to [1,2,1]. Return the minimum number of operations required. Input Format n arr[0] arr[1] ... arr[n-1] Output Format minimum number of operations Constraints 1 <= n <= 2 * 10^5 -10^9 <= arr[i] <= 10^9 Example 1 Input: 4 1 2 1 3 Output: 1 Explanation: Replace all 2s with 1, obtaining [1,1,1,3]. Example 2 Input: 5 1 2 1 3 2 Output: 2 Explanation: The occurrence ranges of the values overlap, so they must eventually be merged into one block, requiring 2 operations. Example Input 4 1 2 1 3 Output 1