basit_stack.c

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

struct stack{
	int top;
	int count;
	int* arr;
};

void init(struct stack *ptr, int size){
	ptr->top   = -1;
	ptr->count = size;
	ptr->arr   = malloc(sizeof(int) * size);
	
	printf("STACK INITED\n");
	
}

void push(struct stack *ptr, int val){
	
	if(ptr->count == ptr->top){
		printf("STACK FULL");
	}else{
		ptr->top++;
		ptr->arr[ptr->top] = val;
		printf("PUSHED %d TOP:%d\n",val,ptr->top);
	}
}

int pop(struct stack *ptr){
	int x;
	if(ptr->top == -1){
		printf("STACK EMPTY");
	}else{
		x = ptr->arr[ptr->top];
		printf("POPPED %d TOP:%d\n",x,ptr->top);
	}
	
	return x;
}

int main(int argc, char *argv[]) {
	
	struct stack myStack;
	
	init(&myStack,50);
	push(&myStack,1998);
	push(&myStack,1974);
	push(&myStack,12556);
	pop(&myStack);
	push(&myStack,1987);
	
	return 0;
}

infix_to_postfix.c

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


struct stack{
	int top;
	int count;
	char* arr;
};

void init(struct stack *ptr, int size){
	ptr->top   = -1;
	ptr->count = size;
	ptr->arr   = malloc(sizeof(char) * size);
	
	printf("STACK INITED\n");
	
}

void push(struct stack *ptr, char val){
	
	if(ptr->count == ptr->top){
		printf("STACK FULL");
	}else{
		ptr->top++;
		ptr->arr[ptr->top] = val;
		//printf("PUSHED %d TOP:%c\n",val,ptr->top);
	}
}

char pop(struct stack *ptr){
	char x = "";
	if(ptr->top == -1){
		printf("STACK UNDERFLOW");
	}else{
		x = ptr->arr[ptr->top];
		ptr->top -= 1;
		//printf("POPPED %d TOP:%d\n",x,ptr->top);
	}
	
	return x;
}

int isOperator(char op){
	
	switch(op){
		case '+':
		case '-':
		case '*':
		case '/':
			return 1;
			break;
	}
	
	return 0;
}

int getOperatorWeight(char op){
	switch(op){
		case '+':
		case '-':
			return 1;
			break;
		case '*':
		case '/':
			return 2;
			break;
		case ')':
		case '(':
			return 0;
			break;
		default:
			return -1;
			break;
	}
}

char lastest(struct stack *ptr){
	if(ptr->top == -1){
		return -1;
	}
	return ptr->arr[ptr->top];
}

int isEmpty(struct stack *ptr){
	return (ptr->top == -1) ? 1 : 0;
}

int main(int argc, char *argv[]) {
	
	struct stack myStack;
	
	init(&myStack,50);
	
	char ifade[] = "A+B-C+D/R";
	int i;
	for(i = 0;i<9;i++){
		char s = ifade[i];
		
		if(isOperator(s)){
			
			if(isEmpty(&myStack) || s == '('){
				push(&myStack,s);
				continue;
			}
			
			if(s == ')'){
				pop(&myStack);
				while(1){
					char x = pop(&myStack);
					
					if(x == '(')
						break;
					
					printf("%c",x);
				}
				continue;
			}
			
			int weight = getOperatorWeight(s);
			int lastestWeight = getOperatorWeight(lastest(&myStack));
			
			if(lastestWeight >= weight){
				printf("%c",pop(&myStack));
				push(&myStack,s);
			}else{
				push(&myStack,s);
			}
			
		}else{
			printf("%c",s);
		}
		
	}
	
	if(!isEmpty(&myStack)){
		while(!isEmpty(&myStack)){
			printf("%c",pop(&myStack));
		}
	}
	
	return 0;
}