main.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define OP_STATE 0
#define NUM_STATE 1
#define FBRAC_STATE 2
#define BBRAC_STATE 3

typedef void(*TransFunc)(int*, char);

typedef struct
{
	int state;
	TransFunc* fptrs;
	int numStates;

} StateMachine;

int bracDepth = 0;

int isOp(char ch)
{
	if(ch == '+' || ch == '-' || ch == '*' || ch=='/')
		return 1;
	return 0;
}

StateMachine* makeStateMachine(int numStates)
{
	StateMachine* sm = (StateMachine*)malloc(sizeof(StateMachine));
	sm->fptrs = (TransFunc*)malloc(numStates*sizeof(TransFunc));
	sm->numStates = numStates;
	sm->state = 0;
	return sm;
}

void setStateMachineTransFunc(StateMachine* sm, int state, TransFunc func)
{
	TransFunc* ptr = &sm->fptrs[state];
	*ptr = func;
}

void runStateMachine(StateMachine* sm, int input)
{
	int state = sm->state;
	sm->fptrs[state](&sm->state, input);
	//printf("%c, %d\n",(char)input, sm->state);
	if(sm->state < 0 || sm->state >= sm->numStates)
	{
		printf("Sequence not legal\n");
		exit(0);
	}
}

void OpStateTransitionFunction(int* state, char ch)
{
	if(ch == ')' || isOp(ch))
		*state = -1;
	else if(ch == '(')
	{
		*state = FBRAC_STATE;
		bracDepth++;
	}
	else
		*state = NUM_STATE;
}

void NumStateTransitionFunction(int* state, char ch)
{
	if(ch == '(')
		*state = -1;
	else if(ch == ')')
	{
		*state = BBRAC_STATE;
		bracDepth--;
	}
	else if(isOp(ch))
		*state = OP_STATE;
	else
		*state = NUM_STATE;
}

void FBracStateTransitionFunction(int* state, char ch)
{
	OpStateTransitionFunction(state, ch);
}

void BBracStateTransitionFunction(int* state, char ch)
{
	NumStateTransitionFunction(state, ch);
}

int main()
{
	char str[40] = {0};
	StateMachine* sm = makeStateMachine(4);
	bracDepth = 0;
	setStateMachineTransFunc(sm,OP_STATE,OpStateTransitionFunction);
	setStateMachineTransFunc(sm,NUM_STATE,NumStateTransitionFunction);
	setStateMachineTransFunc(sm,FBRAC_STATE,FBracStateTransitionFunction);
	setStateMachineTransFunc(sm,BBRAC_STATE,BBracStateTransitionFunction);
	scanf("%s",str);
	int size = strlen(str);
	for(int i=0;i<size;i++)
	{
		char ch = str[i];
		runStateMachine(sm, ch);
	}

	if(bracDepth != 0)
		printf("Sequence not legal\n");
	else
		printf("Sequence is goof");


}