diff --git a/5.leetcode/src/com/fanxb/common/Q150.java b/5.leetcode/src/com/fanxb/common/Q150.java
index 2123433..90d9bb1 100644
--- a/5.leetcode/src/com/fanxb/common/Q150.java
+++ b/5.leetcode/src/com/fanxb/common/Q150.java
@@ -1,6 +1,8 @@
 package com.fanxb.common;
 
 
+import java.util.Stack;
+
 public class Q150 {
     public void gameOfLife(int[][] board) {
         int m = board.length, n = board[0].length;
@@ -32,6 +34,31 @@ public class Q150 {
         }
     }
 
+
+    public int evalRPN(String[] tokens) {
+        Stack<Integer> stack = new Stack<>();
+        for (String str : tokens) {
+            switch (str) {
+                case "+":
+                    stack.push(stack.pop() + stack.pop());
+                    break;
+                case "-":
+                    stack.push(-stack.pop() + stack.pop());
+                    break;
+                case "*":
+                    stack.push(stack.pop() * stack.pop());
+                    break;
+                case "/":
+                    int num1 = stack.pop(), num2 = stack.pop();
+                    stack.push(num2 / num1);
+                    break;
+                default:
+                    stack.push(Integer.valueOf(str));
+            }
+        }
+        return stack.pop();
+    }
+
     public static void main(String[] args) {
     }
 }
diff --git a/5.leetcode/src/com/fanxb/common/Q155.java b/5.leetcode/src/com/fanxb/common/Q155.java
new file mode 100644
index 0000000..353699b
--- /dev/null
+++ b/5.leetcode/src/com/fanxb/common/Q155.java
@@ -0,0 +1,28 @@
+package com.fanxb.common;
+
+import java.util.LinkedList;
+
+public class Q155 {
+    private LinkedList<Integer[]> stack = new LinkedList<>();
+
+    public Q155() {
+
+    }
+
+    public void push(int val) {
+        int min = stack.isEmpty() ? val : Math.min(stack.getFirst()[1], val);
+        stack.push(new Integer[]{val, min});
+    }
+
+    public void pop() {
+        stack.removeFirst();
+    }
+
+    public int top() {
+        return stack.getFirst()[0];
+    }
+
+    public int getMin() {
+        return stack.getFirst()[1];
+    }
+}
diff --git a/5.leetcode/src/com/fanxb/common/Q224.java b/5.leetcode/src/com/fanxb/common/Q224.java
new file mode 100644
index 0000000..ace54b2
--- /dev/null
+++ b/5.leetcode/src/com/fanxb/common/Q224.java
@@ -0,0 +1,72 @@
+package com.fanxb.common;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Stack;
+
+public class Q224 {
+    public int calculate(String s) {
+        Stack<String> stack = new Stack<>();
+        int len = s.length();
+        for (int i = 0; i < len; i++) {
+            char ch = s.charAt(i);
+            switch (ch) {
+                case ' ':
+                    break;
+                case '(':
+                case '+':
+                case '-':
+                    stack.push(ch + "");
+                    break;
+                case ')':
+                    List<String> strs = new ArrayList<>();
+                    String temp;
+                    while (!(temp = stack.pop()).equals("("))
+                        strs.add(temp);
+                    stack.push(cal(strs).toString());
+                    break;
+                default:
+                    //找到数字
+                    StringBuilder builder = new StringBuilder().append(ch);
+                    for (i = i + 1; i < len; i++) {
+                        char ca = s.charAt(i);
+                        if (ca >= '0' && ca <= '9') builder.append(ca);
+                        else break;
+                    }
+                    i--;
+                    stack.push(builder.toString());
+            }
+        }
+        List<String> strings = new ArrayList<>();
+        while (!stack.isEmpty())
+            strings.add(stack.pop());
+        return cal(strings);
+    }
+
+    private Integer cal(List<String> strs) {
+        int len = strs.size();
+        if (len == 1) return Integer.valueOf(strs.get(0));
+        if (len == 2) return Integer.valueOf(strs.get(1) + strs.get(0));
+        String first = strs.get(len - 1);
+        int i, num1;
+        if (first.equals("-")) {
+            num1 = -1 * Integer.parseInt(strs.get(len - 2));
+            i = len - 3;
+        } else {
+            num1 = Integer.parseInt(first);
+            i = len - 2;
+        }
+        for (; i >= 0; i -= 2) {
+            if (strs.get(i).equals("+")) {
+                num1 += Integer.parseInt(strs.get(i - 1));
+            } else {
+                num1 -= Integer.parseInt(strs.get(i - 1));
+            }
+        }
+        return num1;
+    }
+
+    public static void main(String[] args) {
+        System.out.println(new Q224().calculate("-2+1"));
+    }
+}
diff --git a/5.leetcode/src/com/fanxb/common/Q71.java b/5.leetcode/src/com/fanxb/common/Q71.java
new file mode 100644
index 0000000..4da4230
--- /dev/null
+++ b/5.leetcode/src/com/fanxb/common/Q71.java
@@ -0,0 +1,25 @@
+package com.fanxb.common;
+
+import java.util.List;
+import java.util.Stack;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class Q71 {
+    public String simplifyPath(String path) {
+        Stack<String> stack = new Stack<>();
+        List<String> strs = Stream.of(path.split("/+")).filter(item -> !item.isEmpty()).collect(Collectors.toList());
+        for (String str : strs) {
+            switch (str) {
+                case ".":
+                    break;
+                case "..":
+                    if (!stack.isEmpty()) stack.pop();
+                    break;
+                default:
+                    stack.push(str);
+            }
+        }
+        return stack.isEmpty() ? "/" : stack.stream().map(item -> "/" + item).collect(Collectors.joining());
+    }
+}