C + + implementation of infix expression evaluation code __c++

The infix expression string is given and the value is calculated.

Main ideas:

1. The lexical analysis of the string, the analysis results stored to two-yuan array, with the two-element array storage infix expression.

2. Convert infix expression to suffix expression.

3. Use the stack to evaluate the suffix expression.

Characteristics:

A space that can be removed from a string.

can identify more than two digits of integer data calculation, the operator is mainly (+,-,x,/).

Code Run Results:

Infix expression examples are: 12+3* (8/2);

#include <iostream> #include <cstring> using namespace std;
#define the longest length char strtoken[maxsize] of the expression of maxSize-buffer[maxsize];//char;
	typedef struct line{unsigned short id;
Short indexoftable;
};
struct line data[maxsize];
int inttable[maxsize];
Short flagofinttable = 0;

Short flagofstruct = 0;
struct line stackofep[maxsize];//storage suffix expression short stackofid[maxsize];//store symbol short COUNTOFEP = 0;

Short Countofid = 0;
Const short INTEGER = 1;
Const short LEFT_B = 3;
Const short RIGHT_B = 4;
Const short PLUS = 6;

Const short Minux = 7;
Const short MULTIPLY = 9;

Const short DIVIDE = 10;
	void Deleblank (const char* str) {//clear string space for char *temp = buffer;
	if (0 = *str) {*temp = ' ";
				while (*STR) {if (*str = = ") {str++;
			Continue 
	} *temp++ = *str++;
} *temp = ' I ';
	} void Init (char *str) {for (Short i = 0;i <=strlen (str); i++) {*str = 0;
	} void Wordanalyse (const char* str) {const char *start = str;//character start pointer const char *search;//search pointer char *temp; WhilE (*start) {search = start;
		temp = strtoken;//loop once, the temp pointer is corrected to point to Strtoken first address.	
			if (IsDigit (*search)!= 0) {//is a number when the return value is 4 while (IsDigit (*search)!= 0) {*temp++ = *search++;
			} *temp = ' I ';
			Inttable[flagofinttable] = atoi (strtoken);
			Convert string to int, atof (); itoa (int value,char*s1,int radix) data[flagofstruct].id = INTEGER;
			data[flagofstruct].indexoftable = flagofinttable;
			Init (strtoken);//reinitialize flagofstruct++;
			flagofinttable++;
		start = search;
			else if (*start = = ' + ') {data[flagofstruct].id = PLUS;
			data[flagofstruct].indexoftable =-1;
			flagofstruct++;
			start++;
			else if (*start = = '-') {data[flagofstruct].id = Minux;
			data[flagofstruct].indexoftable =-1;
			flagofstruct++;
		start++;
			else if (*start = = ' * ') {data[flagofstruct].id = MULTIPLY;
			data[flagofstruct].indexoftable =-1;
			flagofstruct++;
			start++;
			else if (*start = = '/') {data[flagofstruct].id = DIVIDE;
			data[flagofstruct].indexoftable =-1;flagofstruct++;
		start++;
			else if (*start = = Data[flagofstruct].id = Left_b;
			data[flagofstruct].indexoftable =-1;
			flagofstruct++;
		start++;
			else if (*start = =) ') {data[flagofstruct].id = Right_b;
			data[flagofstruct].indexoftable =-1;
			flagofstruct++;
		start++;
} else{start++}} void Traverse () {//convert infix expression to suffix expression for (int i = 0;i <flagofstruct;i++) {if (data[i].id = = INTEGER) {Stackofe
		p[countofep++] = data[i];//If it is a number, direct pressure into the suffix expression.
					else if (data[i].id >=plus&&data[i].id <= DIVIDE) {//if is the operator symbol while (true) {if (Countofid = 0) {
					stackofid[countofid++] = data[i].id;
				Break
				else if (Data[i].id-stackofid[countofid] >= 2) {stackofid[countofid++] = data[i].id;//into stack break;
					} else{stackofep[countofep].id = stackofid[--countofid];//out Stack stackofep[countofep].indexoftable =-1;
				countofep++; else if (data[i].id = left_b) {//Stackofid[countofid++] = data[i].id; If else if (data[i].id = = Right_b) {while (true) {//until there is an opening parenthesis, the pop-up loop if (stackofid[countofid-1] = = Left_b) {//must be reduced by one, otherwise the logic
					Error.
				countofid--;//out stack break;
				} if (Countofid = = 0) {break;
				} stackofep[countofep].id = Stackofid[--countofid];
				stackofep[countofep].indexoftable =-1;
			countofep++;
				The contents of all the symbol stacks are released and added to the suffix while (countofid) {stackofep[countofep].id = Stackofid[--countofid] When the data entry ends;
				stackofep[countofep].indexoftable =-1;
			countofep++;
	COMPUTE suffix expression int compute () {short tempptr = 0;
	int number[120]; for (int i = 0;i <countofep;i++) {if (stackofep[i].id = INTEGER) {number[tempptr++] = Inttable[stackofep[i].indexof
		Table];
			else if (stackofep[i].id = = PLUS) {int a = Number[--tempptr];
			int b = Number[--tempptr];
		number[tempptr++] = B + A;
			else if (stackofep[i].id = = minux) {int a = Number[--tempptr];
			int b = Number[--tempptr];
		number[tempptr++] = b-a; } else if (stackofep[i].id = = MULTIPLY) {int a = Number[--tempptr];
			int b = Number[--tempptr];
		number[tempptr++] = b * A;
			else if (stackofep[i].id = = DIVIDE) {int a = Number[--tempptr];
			int b = Number[--tempptr];
		number[tempptr++] = b/a;
} return *number; void display () {for (int i = 0;i <flagofstruct;i++) {if (data[i].id = INTEGER) {printf ("%d"), Inttable[data[i].indexof
		Table]);
		else if (data[i].id = = PLUS) {printf ("+");}
		else if (data[i].id = = Minux) {printf ("-");}
		else if (data[i].id = = MULTIPLY) {printf ("*");}
		else if (data[i].id = = DIVIDE) {printf ("/");}
		else if (data[i].id = = left_b) {printf ("(");}
		else if (data[i].id = = right_b) {printf (")");}
	else{printf ("\ n");} } void Displayep () {for (int i = 0;i <countofep;i++) {if (stackofep[i].id = = INTEGER) {printf ("%d", INTTABLE[STACKOFEP
		[i].indexoftable]);}
		else if (stackofep[i].id = = PLUS) {printf ("+");}
		else if (stackofep[i].id = = Minux) {printf ("-");} else if (stackofep[i].id = = MULTIPLY) {printf ("*");}
		else if (stackofep[i].id = = DIVIDE) {printf ("/");}
		else if (stackofep[i].id = = left_b) {printf ("(");}
		else if (data[i].id = = right_b) {printf (")");}
	else{printf ("\ n");}
	int main () {//test Wordanalytse () char str[20] = "12+3* (8/2)";
	Deleblank (str);
	printf (buffer);
	Wordanalyse (buffer);
	Traverse ();
	Displayep ();
	printf ("\ n");
	printf ("%d\n", compute ());
return 0;
 }