12230-crossing rivers (probability)

Ultraviolet A 12230-crossing rivers

Question Link

A: Given several rivers, each river has a boat sailing back and forth. When a day goes out, the boat is in a random position. Now the expected time is required from A to B.

Train of Thought: The worst expectation for each river is that the ship has just driven 3l/V, and the best is to ship the ship directly L/V. The expectation is 4l/V/2 = 2L/v, the answer is the time when the land is migrated.

Code:

# Include <stdio. h> # include <string. h> int N; double D, P, L, V; int main () {int CAS = 0; while (~ Scanf ("% d % lf", & N, & D) & N | D) {While (n --) {scanf ("% lf ", & P, & L, & V); D = D-L + L * 2/V;} printf ("case % d: %. 3lf \ n ", ++ cas, d);} return 0 ;}