Solution.cpp

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int minimumFlips(TreeNode* root, bool result) {
        function<pair<int, int>(TreeNode*)> dfs = [&](TreeNode* root) -> pair<int, int> {
            if (!root) {
                return {1 << 30, 1 << 30};
            }
            int x = root->val;
            if (x < 2) {
                return {x, x ^ 1};
            }
            auto [l0, l1] = dfs(root->left);
            auto [r0, r1] = dfs(root->right);
            int a = 0, b = 0;
            if (x == 2) {
                a = l0 + r0;
                b = min({l0 + r1, l1 + r0, l1 + r1});
            } else if (x == 3) {
                a = min({l0 + r0, l0 + r1, l1 + r0});
                b = l1 + r1;
            } else if (x == 4) {
                a = min(l0 + r0, l1 + r1);
                b = min(l0 + r1, l1 + r0);
            } else {
                a = min(l1, r1);
                b = min(l0, r0);
            }
            return {a, b};
        };
        auto [a, b] = dfs(root);
        return result ? b : a;
    }
};