问题描述
四则运算表达式求值，将四则运算表达式用中缀表达式，然后转换为后缀表达式，并计算结果。
1 #include<stdio.h> 2 #include<stdlib.h> 3 #include<string.h> 4 #include<string> 5 #include<sstream> 6 #include<fstream> 7 #include<iostream> 8 #define TRUE 1 9 #define FALSE 0 10 #define MAXNUM 1000 11 using namespace std; 12 string str1; 13 typedef int DataType; 14 15 16 17 struct BinTreeNode; 18 typedef struct BinTreeNode*PBinTreeNode; 19 struct BinTreeNode 20 { 21 DataType data; 22 PBinTreeNode left; 23 PBinTreeNode right; 24 }; 25 typedef struct BinTreeNode*BinTree; 26 //typedef BinTree*PBinTree; 27 28 int toTree(BinTree* btree,const char *exp,int len) 29 { 30 31 char c; 32 int last,i,bracket; 33 bool have_bracket=FALSE; 34 int num,isnum,nint; 35 int tag1,tag2; 36 37 38 if(exp[0]=='('&&exp[len-1]==')') 39 return toTree(btree,exp+1,len-2); 40 41 bracket=0; 42 last=len; 43 for(i=len-1;i>=0;i--) 44 { 45 c=exp[i]; 46 if(c==')') 47 { 48 have_bracket=TRUE; 49 bracket++; 50 } 51 if(c=='(') bracket--; 52 if(bracket<0) 53 { 54 *btree=NULL; 55 return FALSE; 56 } 57 if(bracket>0) continue; 58 if(c=='+'||c=='-') 59 if(last==len||exp[last]=='*'||exp[last]=='/') 60 last=i; 61 if(c=='*'||c=='/') 62 if(last==len) 63 last=i; 64 } 65 // printf("last %d ",last); 66 if(bracket!=0) return FALSE; 67 68 if(last==len) 69 { 70 if(have_bracket==TRUE) 71 { 72 *btree=NULL; 73 return FALSE; 74 } 75 nint=0; 76 isnum=FALSE; 77 num=0; 78 for(i=0;i<len;i++) 79 { 80 c=exp[i]; 81 switch(c) 82 { 83 case'0':case'1':case'2':case'3':case'4': 84 case'5':case'6':case'7':case'8':case'9': 85 if(isnum==FALSE) 86 { 87 num=c-'0'; 88 isnum=TRUE; 89 nint++; 90 } 91 else 92 { 93 num=num*10+c-'0'; 94 } 95 break; 96 case' ':case' ':case' ': 97 isnum=FALSE; 98 break; 99 default: 100 *btree=NULL; 101 return FALSE; 102 } 103 } 104 if(nint!=1) 105 { 106 *btree=NULL; 107 return FALSE; 108 } 109 *btree=(BinTree)malloc(sizeof(struct BinTreeNode)); 110 (*btree)->data=num; 111 (*btree)->left=NULL; 112 (*btree)->right=NULL; 113 return TRUE; 114 } 115 *btree=(BinTree)malloc(sizeof(struct BinTreeNode)); 116 (*btree)->data=exp[last]; 117 118 tag1 =toTree(&(*btree)->left,exp,last); 119 tag2 =toTree(&(*btree)->right,exp+last+1,len-last-1); 120 if(tag1==TRUE&&tag2==TRUE) return TRUE; 121 return FALSE; 122 } 123 124 int cal(BinTree btree,int*result) 125 { 126 127 int result1,result2; 128 if(btree==NULL) return FALSE; 129 if(btree->left==NULL&&btree->right==NULL) 130 { 131 *result=btree->data; 132 return TRUE; 133 } 134 if(btree->left==NULL||btree->right==NULL) 135 return FALSE; 136 137 switch(btree->data) 138 { 139 140 141 case'+': 142 //cout<<"+"<<endl; 143 if(cal(btree->left,&result1)==FALSE) return FALSE; 144 if(cal(btree->right,&result2)==FALSE) return FALSE; 145 *result=result1+result2; 146 return TRUE; 147 case'-': 148 //cout<<"-"<<endl; 149 if(cal(btree->left,&result1)==FALSE) return FALSE; 150 if(cal(btree->right,&result2)==FALSE) return FALSE; 151 *result=result1-result2; 152 return TRUE; 153 case'*': 154 //cout<<"*"<<endl; 155 if(cal(btree->left,&result1)==FALSE) return FALSE; 156 if(cal(btree->right,&result2)==FALSE) return FALSE; 157 *result=result1*result2; 158 return TRUE; 159 160 case'/': 161 //cout<<"/"<<endl; 162 if(cal(btree->left,&result1)==FALSE) return FALSE; 163 if(cal(btree->right,&result2)==FALSE) return FALSE; 164 *result=result1/result2; 165 return TRUE; 166 default: 167 return FALSE; 168 } 169 } 170 171 void lastOrder(BinTreeNode *btree){ 172 173 174 if(btree){ 175 176 lastOrder(btree->left); 177 lastOrder(btree->right); 178 if((btree->data=='+')&&(btree->left!=NULL)&&(btree->right!=NULL)) 179 {cout<<'+';str1+='+';} 180 else if((btree->data=='-')&&(btree->left!=NULL)&&(btree->right!=NULL)) 181 {cout<<'-';str1+='-';} 182 else if((btree->data=='*')&&(btree->left!=NULL)&&(btree->right!=NULL)) 183 {cout<<'*';str1+='*';} 184 else if((btree->data=='/')&&(btree->left!=NULL)&&(btree->right!=NULL)) 185 {cout<<'/';str1+='/';} 186 else 187 {cout<<btree->data<<" ";stringstream ch;ch<<btree->data;string tem;ch>>tem;str1+=tem;str1+=' ';} 188 189 } 190 // in.close(); 191 } 192 193 int main() 194 { 195 char c,exp[MAXNUM]; 196 int result; 197 BinTree btree; 198 // printf("Please input the expression:"); 199 fstream in; 200 in.open("exp"); 201 cout<<"从文件中读取中缀表达式"<<endl; 202 string str; 203 getline(in,str); 204 strcpy(exp,str.c_str()); 205 if(toTree(&btree,exp,strlen(exp))==FALSE) 206 { 207 in<<"Wrong input! "; 208 209 210 211 212 } 213 else{ 214 lastOrder(btree); 215 cout<<endl; 216 // cout<<str1<<endl; 217 in<<"---"<<str1<<endl; 218 if(cal(btree,&result)==TRUE) in<<result<<endl; 219 else in<<"Wrong input! "; 220 221 222 cout<<result<<endl; 223 } 224 in.close(); 225 226 }