init

1F.py

@@ -0,0 +1,27 @@
+n = int(input())
+edges = [input().strip() for _ in range(n - 1)]
+R_in = [0] * n
+R_out = [0] * n
+B_in = [0] * n
+B_out = [0] * n
+for i in range(n - 1):
+    row = edges[i]
+    for j_idx, color in enumerate(row):
+        j = i + 1 + j_idx
+        if color == 'R':
+            R_out[i] += 1
+            R_in[j] += 1
+        else:
+            B_out[i] += 1
+            B_in[j] += 1
+t_mixed_x2 = 0
+s_in_out = 0
+for v in range(n):
+    road_R = R_in[v] + R_out[v]
+    road_B = B_in[v] + B_out[v]
+    t_mixed_x2 += road_R * road_B
+    s_in_out += R_in[v] * B_out[v] + B_in[v] * R_out[v]
+if t_mixed_x2 // 2 == s_in_out:
+    print("YES")
+else:
+    print("NO")