117 lines
1.9 KiB
C
117 lines
1.9 KiB
C
#include <stdio.h>
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#include <string.h>
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#define MAX_SIZE 100
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char stack[MAX_SIZE];
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int top = -1;
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void push(char item)
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{
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if (top >= MAX_SIZE - 1)
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{
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printf("Stack Overflow\n");
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return;
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}
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stack[++top] = item;
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}
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char pop()
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{
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if (top < 0)
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{
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printf("Stack Underflow\n");
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return -1;
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}
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return stack[top--];
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}
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int precedence(char symbol)
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{
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switch (symbol)
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{
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case '^':
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return 3;
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case '*':
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case '/':
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return 2;
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case '+':
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case '-':
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return 1;
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default:
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return 0;
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}
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}
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void reverse(char *str)
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{
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int len = strlen(str);
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int i, j;
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char temp;
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for (i = 0, j = len - 1; i < j; i++, j--)
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{
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temp = str[i];
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str[i] = str[j];
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str[j] = temp;
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}
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}
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int isalnum(char c)
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{
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return ((c >= '0' && c <= '9') || (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z'));
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}
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void infixToPrefix(char infix[], char prefix[])
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{
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char symbol, temp[2];
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int i, j = 0;
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reverse(infix);
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for (i = 0; infix[i] != '\0'; i++)
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{
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symbol = infix[i];
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if (isalnum(symbol))
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{
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prefix[j++] = symbol;
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}
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else if (symbol == ')')
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{
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push(symbol);
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}
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else if (symbol == '(')
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{
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while ((temp[0] = pop()) != ')')
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{
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prefix[j++] = temp[0];
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}
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}
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else
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{
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while (top > -1 && precedence(stack[top]) > precedence(symbol))
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{
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prefix[j++] = pop();
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}
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push(symbol);
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}
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}
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while (top > -1)
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{
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prefix[j++] = pop();
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}
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prefix[j] = '\0';
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reverse(prefix);
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}
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int main()
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{
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char infix[MAX_SIZE], prefix[MAX_SIZE];
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printf("Enter infix expression: ");
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gets(infix);
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infixToPrefix(infix, prefix);
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printf("Prefix expression: %s\n", prefix);
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return 0;
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}
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