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py3-coder · py3-coder · commit dc736c0684b2 · 2024-10-20T23:44:14.000+05:30
diff --git a/1106-parsing-a-boolean-expression/1106-parsing-a-boolean-expression.java b/1106-parsing-a-boolean-expression/1106-parsing-a-boolean-expression.java
@@ -0,0 +1,25 @@
+class Solution {
+    public boolean parseBoolExpr(String expression) {
+         Deque<Character> stk = new ArrayDeque<>();
+        for (int i = 0; i < expression.length(); ++i) {
+            char c = expression.charAt(i);
+            if (c == ')') {
+                Set<Character> seen = new HashSet<>();
+                while (stk.peek() != '(')
+                    seen.add(stk.pop());
+                stk.pop();// pop out '('.
+                char operator = stk.pop(); // get operator for current expression.
+                if (operator == '&') {
+                    stk.push(seen.contains('f') ? 'f' : 't'); // if there is any 'f', & expression results to 'f'
+                }else if (operator == '|') {
+                    stk.push(seen.contains('t') ? 't' : 'f'); // if there is any 't', | expression results to 't'
+                }else { // ! expression.
+                    stk.push(seen.contains('t') ? 'f' : 't'); // Logical NOT flips the expression.
+                }
+            }else if (c != ',') {
+                stk.push(c);
+            }
+        }
+        return stk.pop() == 't';
+    }
+}
