1007. Minimum Domino Rotations For Equal Row.cpp

1007. Minimum Domino Rotations For Equal Row.cpp

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+class Solution {
+public:
+    int minDominoRotations(vector<int>& tops, vector<int>& bottoms) {
+        const int n = tops.size();
+
+        // Try to make all values equal to tops[0] or bottoms[0]
+        int X=tops[0], Y=bottoms[0];
+        int swapXT=0, swapXB=0;
+        int swapYT=0, swapYB=0;
+
+        bool hasX=1, hasY=1;
+
+        for (int i=0; i<n; i++) {
+            // Check for candidate X
+            if (hasX) {
+                if (tops[i]!=X && bottoms[i]!=X) 
+                    hasX=0;
+                else {
+                    if (tops[i]!=X) swapXT++;
+                    if (bottoms[i]!=X) swapXB++;
+                }
+            }
+
+            // Check for candidate Y
+            if (hasY) {
+                if (tops[i]!=Y && bottoms[i]!=Y) 
+                    hasY=0;
+                else {
+                    if (tops[i]!=Y) swapYT++;
+                    if (bottoms[i]!=Y) swapYB++;
+                }
+            }
+
+            // Early exit if both invalid
+            if (!hasX && !hasY) return -1;
+        }
+
+        int ans=INT_MAX;
+        if (hasX) ans=min(ans, min(swapXT, swapXB));
+        if (hasY) ans=min(ans, min(swapYT, swapYB));
+
+        return ans;
+    }
+};