1 #include <iostream> 2 #include <cstring> 3 #include <cstdio> 4 #include <map> 5 #include <algorithm> 6 using namespace std; 7 const int Ni = 2000; 8 class calcu 9 { 10 public: 11 //传入表达试 12 void init(char *str) 13 { 14 s=str; 15 nc=0;len=strlen(s); 16 build_tree(0,len); 17 } 18 //代入数值计算 19 double calc(int *arr) 20 { 21 int i,j,k; 22 //注意字母是小写 23 for(k=i=0;i<len;i++) if(s[i]>='a'&&s[i]<='z') 24 ch[k++]=s[i]; 25 sort(ch,ch+k); 26 for(j=i=0;i<k;i++) if(ch[j]!=ch[i]) ch[++j]=ch[i]; 27 m.clear(); 28 for(i=0;i<=j;i++) 29 m[ch[i]]=arr[i]; 30 top=-1; 31 query(1); 32 return shu[0]; 33 } 34 private: 35 map<char,double> m; 36 int lch[Ni],rch[Ni]; 37 char op[Ni],*s,ch[Ni]; 38 int top,nc,len; 39 double shu[Ni]; 40 int build_tree(int x,int y) 41 { 42 int i,u,c1=-1,c2=-1,p=0; 43 if(y-x==1) 44 { 45 u=++nc; 46 lch[u]=rch[u]=0; 47 op[u]=s[x]; 48 return u; 49 } 50 for(i=x; i<y; i++) 51 { 52 switch(s[i]) 53 { 54 case '(':p++;break; 55 case ')':p--;break; 56 case '+': 57 case '-':if(!p) c1=i; 58 break; 59 case '*': 60 case '/':if(!p) c2=i; 61 break; 62 } 63 } 64 if(c1<0) c1=c2; 65 if(c1<0) return build_tree(x+1,y-1); 66 u=++nc; 67 lch[u]=build_tree(x,c1); 68 rch[u]=build_tree(c1+1,y); 69 op[u]=s[c1]; 70 return u; 71 } 72 void query(int i) 73 { 74 double ans; 75 if(lch[i]) 76 query(lch[i]); 77 if(rch[i]) 78 query(rch[i]); 79 if(op[i]=='+') 80 { 81 ans=shu[top]+shu[top-1]; 82 top--; 83 shu[top]=ans; 84 return; 85 } 86 if(op[i]=='-') 87 { 88 ans=shu[top-1]-shu[top]; 89 top--; 90 shu[top]=ans; 91 return; 92 } 93 if(op[i]=='*') 94 { 95 ans=shu[top-1]*shu[top]; 96 top--; 97 shu[top]=ans; 98 return; 99 } 100 if(op[i]=='/') 101 { 102 ans=shu[top-1]/shu[top]; 103 top--; 104 shu[top]=ans; 105 return; 106 } 107 shu[++top]=m[op[i]]; 108 } 109 }qr; 110 int arr[20]; 111 char s[Ni]; 112 int main() 113 { 114 int i,n; 115 while(scanf("%d",&n),n) 116 { 117 for(i=0;i<n;i++) scanf("%d",arr+i); 118 scanf("%s",s); 119 qr.init(s); 120 printf("%lf\n",qr.calc(arr)); 121 } 122 return 0; 123 }
计算a=3,b=2,c=5时表达试a+b+(a*c+c-a)-c-b的值
输入样列：
3
3 2 5
a+b+(a*c+c-a)-c-b
输出：
15