Merge pull request chipbk10#108 from chipbk10/Stack

Solve Problem 155 - Min Stack

Author: chipbk10

src/stack/Problem155_MinStack.java

@@ -0,0 +1,32 @@
+package stack;
+
+import java.util.Stack;
+
+public class Problem155_MinStack {
+
+    class MinStack {
+
+        Stack<int[]> stack = new Stack<>();
+
+        /** initialize your data structure here. */
+        public MinStack() {
+        }
+
+        public void push(int x) {
+            int min = (stack.isEmpty()) ? x : Math.min(x, getMin());
+            stack.push(new int[] {x, min});
+        }
+
+        public void pop() {
+            stack.pop();
+        }
+
+        public int top() {
+            return stack.peek()[0];
+        }
+
+        public int getMin() {
+            return stack.peek()[1];
+        }
+    }
+}