# include 
#include 
#include 
# define TRUE 1 
# define FALSE 0 
# define MAXNUM 1000 
Typedef int DataType. 
Struct BinTreeNode; 
Typedef struct BinTreeNode * PBinTreeNode; 
Struct BinTreeNode 
{
DataType info; 
PBinTreeNode llink; 
PBinTreeNode rlink; 
}; 
Typedef struct BinTreeNode * BinTree; 
Typedef BinTree * PBinTree; 
Int extoBinTree (PBinTree pbtree, const char * ex, int n) 
/* from infix expression ex (of length n) create a binary tree, if a legal expression, it returns TRUE, and the algorithm at the end of the * pbtree storing the addresses of root node of the binary tree; Otherwise it returns FALSE */
{
char c; 
Int index, I, bracket; 
Int have_bracket=FALSE;/* record whether the expression contains parentheses */
Int num, state_int nint; 
Int tag1 and tag2. 
If (ex [0]=='| | the ex [0]==' \ t '| | the ex [0]==' \ n ') 
Return extoBinTree (pbtree, ex + 1, n - 1);/* ignore to the left of the number of null character */
If (ex [n - 1]=='| | the ex [0]==' \ t '| | the ex [0]==' \ n ') 
Return extoBinTree (pbtree, ex, n - 1);/* */ignore the right number of null character 
If (ex [0]=='(' & amp; & The ex [n - 1]==') ') 
Return extoBinTree (pbtree, ex + 1, n - 2);/* ignore paired parentheses around */
Bracket=0; 
The index=n; 
For (I=n - 1; i>=0; I -)/* from the forward search, to find the first is not the lowest priority in parentheses operator */
{
C=the ex [I]; 
If (c==') ')/* into a layer of */brackets 
{
Have_bracket=TRUE; 
Bracket++; 
} 
If (c=='(') bracket -; Layer/* a */brackets 
If (bracket<0)/* brackets do not match, expression of illegal */
{
* pbtree=NULL; 
return FALSE; 
} 
If (bracket> 0) continue;/* if the current position in a layer of parentheses, direct search next position */
If (c=='+' | | c=='-') 
If (index==n | | the ex [index]=='*' | | the ex [index]=='/') 
index=i; 
If (c=='*' | | c=='/') 
If (index==n) 
index=i; 
} 
If (bracket!=0) return FALSE./* brackets do not match, expression of illegal */
If (index==n)/* suggests that this is a only a several empty expression of the characters, Numbers and accordingly to create a tree contains only a root node of the binary tree */
{
If (have_bracket==TRUE) 
{
* pbtree=NULL; 
return FALSE; 
}/* should not contain */brackets 
Nint=0;/* nint record expression contains the integer number of */
State_int=FALSE;/* state_int record whether the current read character is numeric characters */
num=0; 
for(i=0; i{
C=the ex [I]; 
The switch (c) 
{
Case '0' case '1' : case '2' : case: '3' case '4' : 
Case '5' : case '6' : case '7' : case '8' : case '9' : 
If (state_int==FALSE) 
{
Num=c - '0'; 
State_int=TRUE; 
Nint++; 
} 
The else 
{
Num=num * 10 + c - '0'; 
} 
break; 
Case 'case' \ t ': case' \ n ': 
State_int=FALSE; 
break; 
Default:/* the illegal characters */
* pbtree=NULL; 
return FALSE; 
} 
} 
If (nint! 
=1){
* pbtree=NULL; 
return FALSE; 
} 
* pbtree=(BinTree) malloc (sizeof (struct BinTreeNode)); 
(* pbtree) - & gt; Info=num; 
(* pbtree) - & gt; Llink=NULL; 
(* pbtree) - & gt; Rlink=NULL; 
Return TRUE;/* successfully created a tree contains only a root node of the binary tree */
} 
* pbtree=(BinTree) malloc (sizeof (struct BinTreeNode)); 
(* pbtree) - & gt; Info=ex [index]; 
Tag1=extoBinTree (& amp; (* pbtree) - & gt; Llink, ex, index);/* number of recursive calls the algorithm to create the left child */
Tag2=extoBinTree (& amp; (* pbtree) - & gt; Rlink, ex + index + 1, n - index - 1);/* number of recursive calls the algorithm to create the right child */
If (tag1==TRUE& & Tag2==TRUE) return TRUE; 
return FALSE; 
} 
Int CAL (BinTree btree, int * presult)/* calculated binary tree btree represents the value of the expression, if a legal expression, it returns TRUE, and the algorithm at the end of the calculation results in the * presult; Otherwise, returns FALSE. */
{
Int result1, result2; 
If (btree==NULL) return FALSE./* empty tree, cannot calculate */
If (btree - & gt; Llink==NULL& & Btree - & gt; Rlink==NULL)/* only one node, direct calculation */
{
* presult=btree - & gt; The info. 
Return TRUE; 
} 
If (btree - & gt; Llink==NULL | | btree - & gt; Rlink==NULL)/* only left subtree or right subtree only, cannot calculate */
return FALSE; 
The switch (btree - & gt; Info) 
{
Case: '+' 
If (CAL (btree - & gt; Llink, & amp; Result1)==FALSE) return FALSE; 
If (CAL (btree - & gt; Rlink, & amp; Result2)==FALSE) return FALSE; 
* presult=result1 + result2; 
Return TRUE; 
In case the '-' : 
If (CAL (btree - & gt; Llink, & amp; Result1)==FALSE) return FALSE; 
If (CAL (btree - & gt; Rlink, & amp; Result2)==FALSE) return FALSE; 
* presult=result1 - result2; 
Return TRUE; 
Case: '*' 
If (CAL (btree - & gt; Llink, & amp; Result1)==FALSE) return FALSE; 
If (CAL (btree - & gt; Rlink, & amp; Result2)==FALSE) return FALSE; 
* presult result2=result1 *; 
Return TRUE; 
Case '/' : 
If (CAL (btree - & gt; Llink, & amp; Result1)==FALSE) return FALSE; 
If (CAL (btree - & gt; Rlink, & amp; Result2)==FALSE) return FALSE; 
* presult=result1/result2; 
Return TRUE; 
Default: 
return FALSE; 
} 
} 
Void delete_BTree (PBinTree ptree) 
{
BinTree temp=(* ptree); 
If (temp==NULL) return; 
Delete_BTree (& amp; (temp & gt; Llink)); 
Delete_BTree (& amp; (temp & gt; Rlink)); 
Free (temp); 
} 
Void getline (char * line, int limit)/* read a line from standard input, as a string line */
{
char c; 
int i=0; 
While (i='\ n'Line [i++]=c; 
Line [I]='\ 0'; 
} 
Int main () 
{
Char c, ex [MAXNUM]; 
Int result, flag=TRUE; 
BinTree btree; 
While (flag==TRUE) 
{
Printf (" please enter the expression: "); 
Getline (ex, MAXNUM);/* */infix expression 
If (extoBinTree (& amp; Btree, ex, strlen (ex))==FALSE) 
{
Printf (" input is wrong! \n"); 
Delete_BTree (& amp; Btree); 
Printf (" \ n to continue? (y/n (n) (is) : "); 
The scanf (" % c ", & amp; C); 
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