ds-lab/program4 at main · vampire-debug/ds-lab · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
#include<stdio.h>
char stack[50];
int top = -1;

void push(char ch)
{
    stack[++top] = ch;
}

char pop()
{
    return(stack[top--]);
}

int prcd(char ch)
{
    int p;
    switch(ch)
    {
    case '$':
    case '^': p = 3;
        break;
    case '*':
    case '/': p = 2;
        break;
    case '+':
    case '-': p = 1;
        break;
    case '(': p = -1;
        break;
    }
    return p;
}

void conversion(char infix[], char postfix[])
{
    int i = 0, p = 0;
    char ch;
    while((ch = infix[i]) != '\0')
    {
        switch(ch)
        {
        default : postfix[p++] = ch;
            break;
        case '(': push(ch);
            break;
        case ')': while(top != -1 && stack[top] != '(')
            postfix[p++] = pop();
            pop();
            break;
        case '*':
        case '/':
        case '+':
        case '-': while(top != -1 && prcd(stack[top]) >= prcd(ch))
                postfix[p++] = pop();
            push(ch);
            break;
        case '$':
        case '^': while(top != -1 && prcd(stack[top]) > prcd(ch))
            postfix[p++] = pop();
            push(ch);
            break;
        }
    i++;
    }
    while (top != -1)
        postfix[p++] = pop();
    postfix[p] = '\0';
}

int main()
{
    char infix[50], postfix[50];
    printf("enter valid infix expression\n");
    scanf("%s", infix);
    conversion(infix, postfix);
    printf("postfix expression= %s\n", postfix);
}