Infix Prefix

[bca072024]

program to convert infix expression to prefix expression

include

include

include

define MAX 20

char STACK[MAX]; int top = -1; int prcd(char); void infix2prefix(char[],char[]); void push(char c) { STACK[++top] = c; } char pop() { return STACK[top--]; } int prcd(char x) { if (x == '^') return 3; else if (x == '*' || x == '/') return 2; else if (x == '+' || x == '-') return 1; else return 0; } void infix2prefix(char infix[], char prefix[]) { char temp, x; int i = 0, j = 0; while (infix[i] != '\0') { temp = infix[i]; if (isalnum(temp)) { prefix[j++] = temp; } else if (temp == '(') { push(temp); } else if (temp == ')') { while ((x = pop()) != '(') { prefix[j++] = x; } } else { while (top != -1 && prcd(STACK[top]) >= prcd(temp)) { prefix[j++] = pop(); } push(temp); } i++; } while (top != -1) { prefix[j++] = pop(); } prefix[j] = '\0'; } int main() { char infix[MAX], prefix[MAX]; printf("Enter infix expression: "); gets(infix); strrev(infix); infix2prefix(infix, prefix); strrev(prefix); printf("Prefix expression: %s\n", prefix); return 0; }