first commit

p102/solution.jl

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+
+function solution(file)
+    triangles_raw = read(file, String)
+    triangles = split(triangles_raw, "\n")
+    c = 0
+    for triangle_raw ∈ triangles
+        triangle = split(strip(triangle_raw), ",")
+        ∠A = atan(parse(Int, triangle[2]), parse(Int, triangle[1]))
+        ∠B = atan(parse(Int, triangle[4]), parse(Int, triangle[3]))
+        ∠C = atan(parse(Int, triangle[6]), parse(Int, triangle[5]))
+
+        ∠AB = ∠(∠A, ∠B)
+        ∠AC = ∠(∠A, ∠C)
+        if (∠AB*∠AC) >= 0 continue end
+
+        ∠BA = ∠(∠B, ∠A)
+        ∠BC = ∠(∠B, ∠C)
+        if (∠BA*∠BC) < 0 c += 1 end
+    end
+    return c
+end
+
+function ∠(∠A, ∠B)
+    ∠AB = mod2pi(∠B - ∠A + π) - π
+    return ∠AB
+end