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%lf%lf", &p, &l, &v);  d = d - l + l * 2 / v;  }  printf("Case %d: %.3lf\n\n", ++cas, d); }return 0;}

12230-crossing rivers (probability)