Add kattis prob kolinje in python3 + notes

kattis/kolinje/solution.py

@@ -0,0 +1,44 @@
+def solve(prev_a, prev_b, curr_a, curr_b):
+    # prev_a + prev_b*X >= curr_a + curr_b*X
+    # X*(prev_b - curr_b) >= curr_a - prev_a
+    if (prev_b - curr_b) == 0:
+        if curr_a > prev_a:
+            return False, None, None
+        else:
+            return True, None, None # curr_a >= prev_a
+    elif (prev_b - curr_b) > 0:
+        lower_x = (curr_a - prev_a) / (prev_b - curr_b)
+        return True, lower_x, None
+    else:
+        upper_x = (curr_a - prev_a) / (prev_b - curr_b)
+        return True, None, upper_x
+
+
+n = int(input())
+
+a = [0 for _ in range(n)]
+b = [0 for _ in range(n)]
+
+for i in range(n):
+    a[i], b[i] = map(int, input().split())
+
+ok = True
+lowers, uppers = [], []
+for i in range(1, n):
+    valid, lower, upper = solve(a[i-1], b[i-1], a[i], b[i])
+    if not valid:
+        ok = False
+        break
+    if lower is not None:
+        lowers.append(lower)
+    if upper is not None:
+        uppers.append(upper)
+
+lower = max(lowers)
+upper = min(uppers)
+if not ok:
+    print(-1)
+elif lower <= upper:
+    print(sum(b)*lower)
+else:
+    print(-1)