2013
11-09

# 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 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

//* @author:
import java.util.Scanner;
public class Main{
public static void main(String[] args){
Scanner cin=new Scanner(System.in);
while(cin.hasNext()){
double wellHeight=cin.nextDouble();
double dayFeet=cin.nextDouble();
double nightFeet=cin.nextDouble();
double fatigue=cin.nextDouble();
if(wellHeight==0)return;
double height=0;
int days;
double temp=0;
for(days=0;height>=0;days++){
temp=dayFeet-dayFeet*(fatigue*0.01)*days;
if(temp< 0)temp=0;
height=height+temp;
if(wellHeight< height){
break;
}
height=height-nightFeet;
}
System.out.println(height< 0 ? "failure on day "+days : "success on day "+(days+1));
}
}
}

1. 如果两个序列的最后字符不匹配（即X [M-1]！= Y [N-1]）
L（X [0 .. M-1]，Y [0 .. N-1]）= MAX（L（X [0 .. M-2]，Y [0 .. N-1]），L（X [0 .. M-1]，Y [0 .. N-1]）
这里写错了吧。

2. 这道题目的核心一句话是：取还是不取。
如果当前取，则index+1作为参数。如果当前不取，则任用index作为参数。

3. Gucci New Fall Arrivals

This is really nice to know. I hope it will be successful in the future. Good job on this and keep up the good work.