poj 1487 Single-Player Games

主要考察表达式的解析和高斯消元！！！

 

  1 #include<iostream>

  2 #include<stdio.h>

  3 #include<algorithm>

  4 #include<iomanip>

  5 #include<cmath>

  6 #include<cstring>

  7 #include<vector>

  8 #define ll __int64

  9 #define pi acos(-1.0)

 10 #define SIZE 1024

 11 using namespace std;

 12 const double eps=1e-8;

 13 inline bool zero(double x)

 14 {

 15     return fabs(x)<eps;

 16 }

 17 struct node

 18 {

 19     int type,val;

 20     node(){}

 21     node(int _type,int _val){

 22         type=_type;

 23         val=_val;

 24     }

 25 }an[SIZE];

 26 vector<int> g[SIZE];

 27 double mat[32][32];

 28 int n,ind;

 29 char *p;

 30 void build(int now)

 31 {

 32     int t,m;

 33     while(*p){

 34         while(*p==' '&&*p) p++;

 35         if(!*p) break;

 36         if((*p>='0'&&*p<='9')||*p=='-'){

 37             ind++;

 38             sscanf(p,"%d%n",&t,&m);

 39             p+=m;

 40             an[ind]=node(0,t);

 41             g[now].push_back(ind);

 42         }

 43         else if(*p=='(')

 44         {

 45             ind++;

 46             an[ind]=node(-1,0);

 47             p++;

 48             g[now].push_back(ind);

 49             build(ind);

 50         }

 51         else if(*p==')')

 52         {

 53             p++;

 54             return;

 55         }

 56         else{

 57             ind++;

 58             an[ind]=node(1,*p-'a');

 59             p++;

 60             g[now].push_back(ind);

 61         }

 62     }

 63 }

 64 void toMat(int now,double tp,int var)

 65 {

 66     double p;

 67     if(g[now].size()) p=tp/g[now].size();

 68     for(int i=0;i<(int)g[now].size();i++){

 69         int x=g[now][i];

 70         if(an[x].type==-1)

 71             toMat(x,p,var);

 72         else{

 73             if(an[x].type==0)

 74                 mat[var][n]+=an[x].val*p;

 75             else{

 76                 mat[var][an[x].val]-=p;

 77             }

 78         }

 79     }

 80 }

 81 void init()

 82 {

 83     ind=0;

 84     memset(an,0,sizeof(an));

 85     for(int i=0;i<SIZE;i++) g[i].clear();

 86 }

 87 void Gauss_line(int a,int b,int col)

 88 {

 89     double mul_a=mat[a][col];

 90     double mul_b=mat[b][col];

 91     for(int i=0;i<=n;i++)

 92         mat[b][i]=mat[b][i]-mat[a][i]*mul_b/mul_a;

 93 }

 94 void Gauss()

 95 {

 96     for(int row=0,col=0;row<n&&col<n;row++,col++){

 97         int ptr=-1;

 98         for(int i=row;i<n;i++)

 99             if(!zero(mat[i][col])){

100                 ptr=i;

101                 break;

102             }

103         if(ptr==-1) continue;

104         else{

105             for(int i=0;i<=n;i++)

106                 swap(mat[row][i],mat[ptr][i]);

107             for(int i=0;i<n;i++)

108                 if(i!=row)

109                     Gauss_line(row,i,col);

110         }

111     }

112 }

113 double getans(int x)

114 {

115     return mat[x][n]/mat[x][x];

116 }

117 bool check(int x)

118 {

119     for(int i=0;i<n;i++)

120         if(i!=x&&!zero(mat[x][i]))

121             return false;

122     return !zero(mat[x][x]);

123 }

124 int main(){

125     int m,i,j,t=1;

126     char cmd[SIZE];

127     while(cin>>n&&n){

128         memset(mat,0,sizeof(mat));

129         printf("Game %d\n",t++);

130         for(int i=0;i<n;i++){

131             init();

132             do{

133                 gets(cmd);

134             }while(*cmd=='\0');

135             p=cmd;

136             while(*p!='(') p++;

137             build(0);

138             toMat(0,1.,i);

139             mat[i][i]+=1.0;

140         }

141         Gauss();

142         for(i=0;i<n;i++){

143             if(check(i))

144                 printf("Expected score for %c = %.3lf\n",'a'+i,getans(i));

145             else

146                 printf("Expected score for %c undefined\n",'a'+i);

147         }

148         printf("\n");

149     }

150     return 0;

151 }

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