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Problem solution · C++

Minimum Operations to Make Array Parity Alternating

Minimum Operations to Make Array Parity Alternating: a C++ solution using direct simulation. Learn the idea, check the complexity, and read the full code, with credit to Kamyu LeetCode Solutions.

Technique
Direct simulation
Source
Kamyu LeetCode Solutions
Length
65 lines
Start with the idea.

Try the problem first. If you get stuck, read the approach below, then write your own solution. The full code is at the bottom.

Approach

Direct simulation

For Minimum Operations to Make Array Parity Alternating, the implementation follows the problem’s operations directly while maintaining only the state needed for the next decision.

  1. Translate each rule into one explicit state update.
  2. Maintain the invariant after every processed item.
  3. Return the accumulated state once all relevant input has been handled.

Code notes

  • 65 lines of C++ from the credited upstream file minimum-operations-to-make-array-parity-alternating.cpp.
  • The implementation visibly relies on sequence storage.
  • 2 loop blocks detected.

Complexity

Count the number and nesting of passes over the input, then include the maintained containers in the memory estimate.

Check the problem constraints before deciding whether this complexity will pass.

Source

Code and credit

This code comes from Kamyu LeetCode Solutions by kamyu104 and is used under the MIT licence.

Open problem ↗Original source ↗
Full codeMinimum Operations to Make Array Parity Alternating · C++C++
Use this to learn the idea, then write your own version.
// Time:  O(n)// Space: O(1) // greedyclass Solution {public:    vector<int> makeParityAlternating(vector<int>& nums) {        static const int POS_INF = numeric_limits<int>::max();        static const int NEG_INF = numeric_limits<int>::min();         const auto& count = [&](int target) {            int cnt = 0;            int mn = POS_INF, mx = NEG_INF;            for (int i = 0; i < size(nums); ++i) {                if ((nums[i] & 1) == ((i & 1) ^ target)) {                    mn = min(mn, nums[i]);                    mx = max(mx, nums[i]);                } else {                    ++cnt;                    mn = min(mn,  nums[i] + 1);                    mx = max(mx,  nums[i] - 1);                }            }            return vector<int>{cnt, size(nums) == 1 ? 0 : (ranges::max(nums) == ranges::min(nums) ? 1 : mx - mn)};        };         return min(count(0), count(1));    }}; // Time:  O(n)// Space: O(1)// greedyclass Solution2 {public:    vector<int> makeParityAlternating(vector<int>& nums) {        static const int POS_INF = numeric_limits<int>::max();        static const int NEG_INF = numeric_limits<int>::min();         const auto& count = [&](int target) {            int cnt = 0;            int mn = ranges::min(nums), mx = ranges::max(nums);            int mn2 = POS_INF, mx2 = NEG_INF;            for (int i = 0; i < size(nums); ++i) {                if ((nums[i] & 1) == ((i & 1) ^ target)) {                    mn2 = min(mn2, nums[i]);                    mx2 = max(mx2, nums[i]);                } else {                    ++cnt;                    if (nums[i] == mn) {                        mn2 = min(mn2, nums[i] + 1);                        mx2 = max(mx2, nums[i] + 1);                    } else if (nums[i] == mx) {                        mn2 = min(mn2, nums[i] - 1);                        mx2 = max(mx2, nums[i] - 1);                    }                }            }            return vector<int>{cnt, mx2 - mn2};        };         return min(count(0), count(1));    }};

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