Create minimum-operations-to-make-the-array-alternating.cpp

Author: kamyu104

C++/minimum-operations-to-make-the-array-alternating.cpp

@@ -0,0 +1,37 @@
+// Time:  O(n)
+// Space: O(n)
+
+// freq table
+class Solution {
+public:
+    int minimumOperations(vector<int>& nums) {
+        const auto& find_top1_and_top2 = [](const auto& cnt) {
+            int top1 = -1, top2 = -1;
+            for (const auto& [k, v] : cnt) {
+                if (top1 == -1 || v >= cnt.at(top1)) {
+                    top2 = top1;
+                    top1 = k;
+                } else if (top2 == -1 || v > cnt.at(top2)) {
+                    top2 = k;
+                }
+            }
+            return make_pair(top1, top2);
+        };
+
+        unordered_map<int, int> even;
+        for (int i = 0; i < size(nums); i += 2) {
+            ++even[nums[i]];
+        }
+        unordered_map<int, int> odd;
+        for (int i = 1; i < size(nums); i += 2) {
+            ++odd[nums[i]];
+        }
+        const auto& [even_top1, even_top2] = find_top1_and_top2(even);
+        const auto& [odd_top1, odd_top2] = find_top1_and_top2(odd);
+        if (even_top1 != odd_top1) {
+            return size(nums) - even[even_top1] - (odd_top1 != -1 ? odd[odd_top1] : 0);
+        }
+        return min(size(nums) - even[even_top1] - (odd_top2 != -1 ? odd[odd_top2] : 0),
+                   size(nums) - odd[odd_top1] - (even_top2 != -1 ? even[even_top2] : 0));
+    }
+};