Time Limit:1000MS Memory Limit:32768KB 64bit IO Format:%I64d & %I64u
Description
For
a few months now, Roy has been assessing the security of various banks
and the amount of cash they hold. He wants to make a calculated risk,
and grab as much money as possible.
His mother, Ola, has decided upon a tolerable
probability of getting caught. She feels that he is safe enough if the
banks he robs together give a probability less than this.
Input
scenario, the first line of input gives a floating point number P, the
probability Roy needs to be below, and an integer N, the number of banks
he has plans for. Then follow N lines, where line j gives an integer Mj
and a floating point number Pj .
Bank j contains Mj millions, and the probability of getting caught from robbing it is Pj .
Output
he can expect to get while the probability of getting caught is less
than the limit set.
Notes and Constraints
0 < T <= 100
0.0 <= P <= 1.0
0 < N <= 100
0 < Mj <= 100
0.0 <= Pj <= 1.0
A bank goes bankrupt if it is robbed, and you may assume that all
probabilities are independent as the police have very low funds.
Sample Input
3
0.04 3
1 0.02
2 0.03
3 0.05
0.06 3
2 0.03
2 0.03
3 0.05
0.10 3
1 0.03
2 0.02
3 0.05
Sample Output
题目给了每个银行的钱和被抓的概率,由于要抢尽量多的钱,所以要保证尽量不被抓,而抢多个银行之后不被抓的概率是抢每一个银行不被抓的概率之 积,我竟然把这一点给忘了!导致我走了许多弯路,思路不能太死啊!dp[]表示抢到下标所对应的钱时,此时不被抓的概率,题目给出了最终不能高于被抓概率 P,不被抓的概率就不能低于(1-P),所以最后只需要逆序遍历dp,找到第一个大于等于1-P的dp[i],就能够保证i最大,即抢到的钱最多。
/* ***********************************************
Author :Mubaixu
File Name :HDU2955.cpp
************************************************ */ #include<stdio.h>
#include<string.h>
#include<iostream>
#include<queue>
#include<algorithm>
using namespace std;
const int maxm=;
const int maxn=;
double dp[maxm];
int value[maxn];
double tp[maxn];
int main(){
int t;
int n;
double p;
scanf("%d",&t);
while(t--){
scanf("%lf%d",&p,&n); int sum=;
for(int i=;i<=n;i++){
scanf("%d%lf",&value[i],&tp[i]);
tp[i]=-tp[i];
sum+=value[i];
}
memset(dp,,sizeof(dp));
dp[]=; for(int i=;i<=n;i++){
for(int j=sum;j>=value[i];j--){
dp[j]=max(dp[j],dp[j-value[i]]*tp[i]);
}
}
for(int i=sum;i>=;i--){
if(dp[i]>(-p)){
printf("%d\n",i);
break;
} } }
return ;
}