动态规划求一定数量骰子和的概率

2018华为实习机试

题目描述：略

动态规划：

f(n,s)=f(n-1,s-1)+f(n-1,s-2)+f(n-1,s-3)+.....+f(n-1,s-6)      至于f(n-1,s-k)是否存在，由Record的getinfo()判断，不存在就设为０

 

 

  1 #include <iostream>
  2 #include<vector>
  3 #include<iomanip>
  4 #include<cmath>
  5 
  6 using namespace std;
  7 class Record{
  8 public:
  9     vector<vector<int>> data;
 10     Record(){}
 11     Record(int s)
 12     {
 13         data.resize(s);
 14         for(int i=0;i<s;++i){
 15             data[i].resize(5*i+6);
 16         }
 17     }
 18     bool addinfo(int dicenum,int sum,int cnt)
 19     {
 20         if(sum>=dicenum && sum<=dicenum*6){
 21             data[dicenum-1][sum-dicenum]=cnt;
 22             return true;
 23         }
 24         else{
 25             return false;
 26         }
 27     }
 28     int getinfo(int dicenum,int sum)
 29     {
 30         if(sum>=dicenum && sum<=dicenum*6){
 31             return data[dicenum-1][sum-dicenum];
 32         }
 33         else{
 34             return 0;
 35         }
 36     }
 37 };
 38 
 39 
 40 int main()
 41 {
 42     int dicenum;
 43     int total;
 44     while(cin >> dicenum){
 45         int smin,smax;
 46         Record rec(dicenum);
 47         total = (int)(0.5+pow(6,dicenum));
 48         for(int i=1;i<=dicenum;++i){
 49             smin = i;
 50             smax = i*6;
 51             if(i==1){
 52                 for(int j=smin;j<=smax;++j){
 53                     rec.addinfo(1,j,1);
 54                 }
 55             }
 56             else{
 57                 for(int j=smin;j<=smax;++j){
 58                     int tempcnt = 0;
 59                     for(int k=1;k<=6;++k){
 60                         tempcnt += rec.getinfo(i-1,j-k);
 61                     }
 62                     rec.addinfo(i,j,tempcnt);
 63                 }
 64             }
 65         }
 66         /*test rec data
 67         for(int i=1;i<=dicenum;++i){
 68             int temp = 0;
 69             cout << i << endl;
 70             for(int j=i;j<=i*6;++j){
 71                 if((temp=rec.getinfo(i,j))!=0){
 72                     cout << temp << " ";
 73                 }
 74             }
 75             cout << endl;
 76         }
 77         */
 78 
 79         /*
 80         output 1: 当数字很大时，结果不对称
 81         double prob = 0;
 82         cout << "[";
 83         for(int i=smin;i<=smax;++i){
 84             prob = (double)(rec.getinfo(dicenum,i)) / total;
 85             cout << "[" << i << ", ";
 86             cout.flags(ios::fixed);
 87             cout.precision(5);
 88             cout << prob << "]";
 89             if(i != smax){
 90                 cout << ", ";
 91             }
 92         }
 93         cout << "]" << endl;
 94         */
 95 
 96         //output 2:使输出结果对称，且减少运算量
 97         vector<double> prob;
 98         prob.resize((smax+smin)/2);
 99         cout << "[";
100         for(int i=smin;i<=(smin+smax)/2;++i){
101             prob[i-smin] = (double)(rec.getinfo(dicenum,i)) / total;
102             cout << "[" << i << ", ";
103             cout.flags(ios::fixed);
104             cout.precision(5);
105             cout << prob[i-smin] << "]" << ", ";
106         }
107         int tempsum = (smin+smax)/2+1;
108         for(int i=prob.size()-1;i>=0;--i){
109             if(i==prob.size()-1){
110                 if((smin+smax)%2!=0){
111                     cout << "[" << tempsum << ", ";
112                     cout.flags(ios::fixed);
113                     cout.precision(5);
114                     cout << prob[i] << "]" << ", ";
115                     tempsum++;
116                 }
117             }
118             else{
119                 cout << "[" << tempsum << ", ";
120                 cout.flags(ios::fixed);
121                 cout.precision(5);
122                 cout << prob[i] << "]";
123                 tempsum++;
124                 if(i!=0){
125                     cout << "], ";
126                 }
127             }
128         }
129         cout << "]" << endl;
130     }
131     return 0;
132 }

 程序缺陷：对于多个测例，没有将之前Record类的信息保留节省计算

posted on 2018-04-19 17:16  CreatorKou  阅读(207)  评论(0)  编辑  收藏  举报

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