1 files changed, 43 insertions, 0 deletions
diff --git a/102.py b/102.py
new file mode 100644
index 0000000..a2108f6
--- /dev/null
+++ b/102.py
@@ -0,0 +1,43 @@
+
+# check if r*(AC) + s*(AB) == P
+
+def point_in_triangle((x_a, y_a), (x_b, y_b), (x_c, y_c), (x_p, y_p)):
+    t = x_c - x_a
+    u = x_b - x_a
+    v = y_c - y_a
+    w = y_b - y_a
+
+    # Cramer's rule
+    detA = t*w - u*v
+    detR = x_p*w - u*y_p
+    detS = t*y_p - x_p*v
+
+    if detA == 0:
+	print "Not solvable"
+
+    r = detR / float(detA)
+    s = detS / float(detA)
+
+    return 0 <= r <= 1 and 0 <= s <= 1 and r + s < 1
+
+
+count = 0
+
+f = open('102.txt', 'r')
+for line in f:
+    line = line.rstrip('\r\n')
+    coords = [ int(x) for x in line.split(',') ]
+
+    # move one point to origin, adjust other points
+    (a1, a2) = (coords[0], coords[1])
+    A = (0, 0)
+    B = (coords[2]-a1, coords[3]-a2)
+    C = (coords[4]-a1, coords[5]-a2)
+    P = (-a1, -a2)
+
+    if point_in_triangle(A, B, C, P):
+	count += 1
+f.close()
+
+print count
+