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DS/C/Lab/Week6/PrefixCheck.c

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+#include <stdio.h>
+#include <string.h>
+
+#define MAX_SIZE 100
+
+int stack[MAX_SIZE];
+int top = -1;
+
+void push(int item) {
+    if (top >= MAX_SIZE - 1) {
+        printf("Stack Overflow\n");
+        return;
+    }
+    stack[++top] = item;
+}
+
+int pop() {
+    if (top < 0) {
+        printf("Stack Underflow\n");
+        return -1;
+    }
+    return stack[top--];
+}
+
+int isOperator(char c) {
+    return (c == '+' || c == '-' || c == '*' || c == '/');
+}
+
+int isDigit(char c) {
+    return (c >= '0' && c <= '9');
+}
+
+int evaluatePrefix(char* expr) {
+    int len = strlen(expr);
+    for (int i = len - 1; i >= 0; i--) {
+        if (isDigit(expr[i])) {
+            push(expr[i] - '0');
+        } else if (isOperator(expr[i])) {
+            int operand1 = pop();
+            int operand2 = pop();
+            switch (expr[i]) {
+                case '+': push(operand1 + operand2); break;
+                case '-': push(operand1 - operand2); break;
+                case '*': push(operand1 * operand2); break;
+                case '/': 
+                    if (operand2 != 0) push(operand1 / operand2);
+                    else {
+                        printf("Error: Division by zero\n");
+                        return -1;
+                    }
+                    break;
+            }
+        }
+    }
+    return pop();
+}
+
+int main() {
+    char expr[MAX_SIZE];
+    printf("Enter prefix expression: ");
+    fgets(expr, MAX_SIZE, stdin);
+    expr[strcspn(expr, "\n")] = 0;  // Remove newline if present
+    
+    int result = evaluatePrefix(expr);
+    if (result != -1) {
+        printf("Result: %d\n", result);
+    }
+    
+    return 0;
+}