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Data Structures/AI Notes/Stack.md

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+# Overview
+
+
+- A stack is ta LIFO list. Meaning "last in first out"
+- Access is allowed only from one end of the stack 
+	- adding an item is called pulsing the stack 
+	- retrieving an item is called popping the stack 
+
+# Typical uses
+
+- Parentheses matching; ()), or (())  
+	- compiler's syntax check for matching braces is implemented by using stack
+
+- The simplest application of a stack is to reverse a word.  
+	• You push a given word to stack - letter by letter - and then pop letters from the stack.  
+
+- Another application is an "undo" mechanism in text editors;  
+	•this operation is accomplished by keeping all text changes in a stack
+
+# Parenthesis count 
+
+- Methodology (logical steps to solve the problem):  
+	- scan expression from left to right;  
+	- when a left parenthesis is encountered, add its position to the stack;  
+- when a right parenthesis is encountered, remove matching position from stack (more example in a moment).  
+
+# try-catch-throw
+
+- When you enter a try block, push the address of this block onto a stack.  
+\
+- When an exception is thrown, pop the try block that is at the top of the stack; if the stack is empty, terminate the program.  
+
+- If the popped try block has no matching catch block, go back to the previous step.  
+
+- If the popped try block has a matching catch block, execute the matching catch block.