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// 核心思想：对于A[0]和B[0]，分别找两列有没有相同元素，且记录A->B交换与B->A交换的次数，当条件满足且到达array最后的min交换值
// 如果有答案，那么就可以直接return，因为不可能有两个min不同的答案，所以没有必要比较
class Solution {
public:
    int minDominoRotations(vector<int>& A, vector<int>& B) {
        int n = A.size();
        // Test for A[0]
        int a_swap = 0, b_swap = 0;
        for (int i = 0; i < n && (A[i] == A[0] || B[i] == A[0]); i++) {
            if (A[i] != A[0]) a_swap++;
            if (B[i] != A[0]) b_swap++;
            if (i == n - 1) return min(a_swap, b_swap);
        }
        // Test for B[0]
        a_swap = 0, b_swap = 0;
        for (int i = 0; i < n && (A[i] == B[0] || B[i] == B[0]); i++) {
            if (A[i] != B[0]) a_swap++;
            if (B[i] != B[0]) b_swap++;
            if (i == n - 1) return min(a_swap, b_swap);
        }
        // Impossible
        return -1;
    }
};