Update MinMaxStack.java

codewithcs · web-flow · commit 24715387f0c2 · 2020-05-06T05:11:28.000+01:00
diff --git a/Medium/MinMaxStack.java b/Medium/MinMaxStack.java
@@ -1 +1,62 @@
 
+package AlgoExpert_Medium;
+
+import java.util.Map;
+import java.util.List;
+import java.util.ArrayList;
+import java.util.HashMap;
+
+public class MinMaxStackConstruction {
+
+	public static void main(String[] args) {
+		
+	}
+
+	  static class MinMaxStack {
+		  
+		List<Map<String, Integer>> minMaxStack = new ArrayList<Map<String, Integer>>() ; 
+		List<Integer> stack = new ArrayList<Integer>(); 
+		  
+		// O(1) time | O(1) space
+	    public int peek() {
+	      return stack.get(stack.size()-1); 
+	    }
+	    
+	    // O(1) time | O(1) space
+	    public int pop() {
+	      minMaxStack.remove(minMaxStack.size()-1); 
+	      return stack.remove(stack.size()-1); 
+	    }
+
+	    // O(1) time | O(1) space
+	    public void push(Integer number) {
+	    	Map<String, Integer> newMinMax = new HashMap<>(); 
+	    	newMinMax.put("min", number);
+	    	newMinMax.put("max", number) ; 
+	    	
+	    	if(!minMaxStack.isEmpty()) {
+	    		Map<String, Integer> lastMinMax = 
+	    				new HashMap<>(minMaxStack.get(minMaxStack.size()-1)); 
+	    		newMinMax.replace("min", Math.min(lastMinMax.get("min"), number) ) ;
+	    		newMinMax.replace("max", Math.max(lastMinMax.get("max"), number) ) ;
+	    	}
+	    	minMaxStack.add(newMinMax) ;
+	    	stack.add(number); 
+	    }
+
+	    // O(1) time | O(1) space
+	    public int getMin() {
+	      return minMaxStack.get(minMaxStack.size()-1).get("min");
+	    }
+
+	 
+	    // O(1) time | O(1) space
+	    public int getMax() {
+	      return minMaxStack.get(minMaxStack.size()-1).get("max");
+	    }
+	    
+	  }
+	
+}
+// All class methods should run in constant time and constant space. 
+
