2013
12-04

The Snail

A snail is at the bottom of a 6-foot well and wants to climb to the top. The snail can climb 3 feet while the sun is up, but slides down 1 foot at night while sleeping. The snail has a fatigue factor of 10%, which means that on each successive day the snail climbs 10% * 3 = 0.3 feet less than it did the previous day. (The distance lost to fatigue is always 10% of the first day’s climbing distance.) On what day does the snail leave the well, i.e., what is the first day during which the snail’s height exceeds 6 feet? (A day consists of a period of sunlight followed by a period of darkness.) As you can see from the following table, the snail leaves the well during the third day.

Day Initial Height Distance Climbed Height After Climbing Height After Sliding
1 0 3 3 2
2 2 2.7 4.7 3.7
3 3.7 2.4 6.1 –

Your job is to solve this problem in general. Depending on the parameters of the problem, the snail will eventually either leave the well or slide back to the bottom of the well. (In other words, the snail’s height will exceed the height of the well or become negative.) You must find out which happens first and on what day.

The input file contains one or more test cases, each on a line by itself. Each line contains four integers H, U, D, and F, separated by a single space. If H = 0 it signals the end of the input; otherwise, all four numbers will be between 1 and 100, inclusive. H is the height of the well in feet, U is the distance in feet that the snail can climb during the day, D is the distance in feet that the snail slides down during the night, and F is the fatigue factor expressed as a percentage. The snail never climbs a negative distance. If the fatigue factor drops the snail’s climbing distance below zero, the snail does not climb at all that day. Regardless of how far the snail climbed, it always slides D feet at night.

For each test case, output a line indicating whether the snail succeeded (left the well) or failed (slid back to the bottom) and on what day. Format the output exactly as shown in the example.

6 3 1 10
10 2 1 50
50 5 3 14
50 6 4 1
50 6 3 1
1 1 1 1
0 0 0 0

success on day 3
failure on day 4
failure on day 7
failure on day 68
success on day 20
failure on day 2

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;

int main(){
double h,u,d,f;
while(~scanf("%lf",&h)&&h){
scanf("%lf%lf%lf",&u,&d,&f);
int day=0;
bool flag=true;
double dist=0,s=u*f/100;
while(1){
day++;
dist+=u;
if(dist>h)break;
dist-=d;
if(dist<0){flag=false;break;};
u-=s;
if(u<0)u=0;
}
if(flag){
printf("success on day %d\n",day);
}else
printf("failure on day %d\n",day);
}
return 0;
}

1. 68的有的是在高架桥上扫街，70也有的是在饭店后厨帮工摘菜，80还有在路口修车的，都是对职业的态度，他们同样辛苦，而且是每天辛苦，而且他们干几年都比不上六小龄童在电视前说几句话，十八九从农村出来打工的除了挨累还要挨骂，20几岁刚毕业的女学生可能还要被领导