HDU5066-Harry And Physical Teacher

Harry And Physical Teacher

                                                           Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)

                                                                                         Total Submission(s): 764    Accepted Submission(s): 408

Problem Description As we all know, Harry Porter learns magic at Hogwarts School. However, learning magical knowledge alone is insufficient to become a great magician. Sometimes, Harry also has to gain knowledge from other certain subjects, such as language, mathematics, English, and even algorithm. 

Today, Harry's physical teacher set him a difficult problem: if a small ball moving with a speed  V0  made a completely elastic collision with a car moving towards the same direction with a speed  V(V<V0) , and the car far outweighs the ball, what was the speed of the small ball after the collision?

This problem was so difficult that Harry hasn't figure out how to solve it. Therefore, he asks you for help. Could you do him this favor?  

Input They are several test cases, you should process to the end of file.

There are two integers  V  and  V0  for each test case. All the integers are 32-bit signed non-negative integers.  

Output For each test case, just output one line that contains an integer indicate the speed of the small ball after the collision.  

Sample Input

0 10
        

Sample Output

-10
        

Source BestCoder Round #14  

Recommend heyang  

题意：有辆汽车正在运动，速度为V0，一个球和车同向运动，速度为V（V >V0）。球会撞向汽车，然后弹性碰撞。假设汽车的质量远大于气球的质量，求球反弹后的速度

解题思路：弹性碰撞，所以利用动能定理和动量定理

#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <algorithm>
#include <queue>
#include <stack>
#include <cmath>
#include <map>
#include <bitset>
#include <set>
#include <vector>
#include <functional>

using namespace std;

#define LL long long
const int INF = 0x3f3f3f3f;

int v,v0;

int main()
{
	while(~scanf("%d%d",&v,&v0))
    {
        printf("%d\n",2*v-v0);
    }
	return 0;
}