hdu 4438 Hunters【数学水题】

Hunters

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1438    Accepted Submission(s): 1083

Problem Description

Alice and Bob are the topmost hunters in the forest, so no preys can escape from them. However, they both think that its hunting skill is better than the other. So they need a match.
In their match, the targets are two animals, a tiger and a wolf. They both know that the tiger is living in the south of the forest and the wolf is living in the north of the forest. They decide that the one who kills the tiger scores X points and who kills the wolf scores Y points. If the one who kills both tiger and wolf scores X+Y points.
Before the match starts, Alice is in the east of the forest and Bob is in the west of the forest. When the match starts, Alice and Bob will choose one of the preys as targets. Because they haven't known the other's choice, maybe they choose the same target. There will be two situations:
(1) If they choose different targets, they both are sure of killing their respective targets.
(2) If they choose the same target, the probability of Alice killing the target is P, and the probability of Bob killing it is 1-P. Then they will hunt for the other prey, also the probability of Alice killing it is P and the probability of Bob killing it is 1-P.
But Alice knows about Bob. She knows that the probability of Bob choosing tiger as his first target is Q, and the probability of choosing wolf is 1-Q. So that Alice can decide her first target to make her expected score as high as possible.

Input

The first line of input contains an integer T (1≤T≤10000), the number of test cases.
Then T test cases follow. Each test case contains X, Y, P, Q in one line. X and Y are integers and 1≤X, Y≤1000000000. P and Q are decimals and 0≤P, Q≤1, and there are at most two digits after decimal point.

Output

For each test case, output the target Alice should choose and the highest expected score she can get, in one line, separated by a space. The expected score should be rounded to the fourth digit after decimal point. It is guaranteed that Alice will have different expected score between choosing tiger and wolf.

Sample Input

3

2 1 0.5 0.5

2 1 0 1

7 7 0.32 0.16

Sample Output

tiger 1.7500

wolf 1.0000

tiger 6.5968

 

题目大意：

有t组数据，每组数据四个元素，分别表示：杀掉老虎的得分，杀掉狼的得分，如果A和B两个人选择同一种动物A获胜的概率，以及B一开始选择杀老虎的概率。问A先选择杀哪一种动物能够获得最大期望得分。

 

思路：

1、先选老虎杀将会得分:X*P*Q+Y*P*Q+X*(1-Q);

2、先选狼杀将会得分：Y*P*(1-Q)+X*P*(1-Q)+Y*Q;

3、比较两者大小，输出最优即可。

Ac代码：

#include<stdio.h>#include<string.h>using namespace std;int main(){    int t;    scanf("%d",&t);    while(t--)    {        int x,y;        double c1,c2;        scanf("%d%d%lf%lf",&x,&y,&c1,&c2);        double hu1,lang1,hu2,lang2;       hu1=x*c1*c2+y*c1*c2+x*(1-c2);       lang1=y*c1*(1-c2)+x*c1*(1-c2)+y*c2;       if(hu1>lang1)       {           printf("tiger %.4lf\n",hu1);       }       else printf("wolf %.4lf\n",lang1);    }    return 0;}