feat: update solutions to lcof problem

Author: yanglbme

lcof/面试题16. 数值的整数次方/README.md

@@ -39,21 +39,15 @@
 
 ```python
 class Solution:
-    cache = {}
     def myPow(self, x: float, n: int) -> float:
-        self.cache = {}
-        return self.pow(x, n)
-
-    def pow(self, x, n):
-        if self.cache.get('{}-{}'.format(x, n)):
-            return self.cache['{}-{}'.format(x, n)]
-        if n == 0: return 1
-        if n == 1: return x
-        if n == -1: return 1 / x
-
-        half = self.pow(x, n // 2)
-        self.cache['{}-{}'.format(x, n // 2)] = half
-        return half * half * self.pow(x, n % 2)
+        if n == 0:
+            return 1
+        if n == 1:
+            return x
+        if n == -1:
+            return 1 / x
+        half = self.myPow(x, n // 2)
+        return half * half * self.myPow(x, n % 2)
 ```
 
 ### **Java**

lcof/面试题16. 数值的整数次方/Solution.java

@@ -1,11 +1,8 @@
 class Solution {
     public double myPow(double x, int n) {
-        if (n == 0)
-            return 1;
-        if (n == 1)
-            return x;
-        if (n == -1)
-            return 1 / x;
+        if (n == 0) return 1;
+        if (n == 1) return x;
+        if (n == -1) return 1 / x;
         double half = myPow(x, n / 2);
         return half * half * myPow(x, n % 2);
     }

lcof/面试题16. 数值的整数次方/Solution.py

@@ -1,16 +1,10 @@
 class Solution:
-    cache = {}
     def myPow(self, x: float, n: int) -> float:
-        self.cache = {}
-        return self.pow(x, n)
-
-    def pow(self, x, n):
-        if self.cache.get('{}-{}'.format(x, n)):
-            return self.cache['{}-{}'.format(x, n)]
-        if n == 0: return 1
-        if n == 1: return x
-        if n == -1: return 1 / x
-
-        half = self.pow(x, n // 2)
-        self.cache['{}-{}'.format(x, n // 2)] = half
-        return half * half * self.pow(x, n % 2)
+        if n == 0:
+            return 1
+        if n == 1:
+            return x
+        if n == -1:
+            return 1 / x
+        half = self.myPow(x, n // 2)
+        return half * half * self.myPow(x, n % 2)

lcof/面试题30. 包含min函数的栈/README.md

@@ -34,22 +34,22 @@ class MinStack:
         """
         initialize your data structure here.
         """
-        self._s1 = []
-        self._s2 = []
+        self.s1 = []
+        self.s2 = []
 
     def push(self, x: int) -> None:
-        self._s1.append(x)
-        self._s2.append(x if len(self._s2) == 0 or self._s2[-1] > x else self._s2[-1])
+        self.s1.append(x)
+        self.s2.append(x if not self.s2 or self.s2[-1] >= x else self.s2[-1])
 
     def pop(self) -> None:
-        self._s1.pop()
-        self._s2.pop()
+        self.s1.pop()
+        self.s2.pop()
 
     def top(self) -> int:
-        return self._s1[-1]
+        return self.s1[-1]
 
     def min(self) -> int:
-        return self._s2[-1]
+        return self.s2[-1]
 
 
 # Your MinStack object will be instantiated and called as such:
@@ -64,29 +64,29 @@ class MinStack:
 
 ```java
 class MinStack {
-    private Stack<Integer> s1;
-    private Stack<Integer> s2;
+    private Deque<Integer> s1;
+    private Deque<Integer> s2;
 
     /** initialize your data structure here. */
     public MinStack() {
-        s1 = new Stack<>();
-        s2 = new Stack<>();
+        s1 = new ArrayDeque<>();
+        s2 = new ArrayDeque<>();
     }
-
+    
     public void push(int x) {
         s1.push(x);
-        s2.push((s2.empty() || s2.peek() > x) ? x : s2.peek());
+        s2.push(s2.isEmpty() || s2.peek() >= x ? x : s2.peek());
     }
-
+    
     public void pop() {
         s1.pop();
         s2.pop();
     }
-
+    
     public int top() {
         return s1.peek();
     }
-
+    
     public int min() {
         return s2.peek();
     }

lcof/面试题30. 包含min函数的栈/Solution.java

@@ -1,16 +1,16 @@
 class MinStack {
-    private Stack<Integer> s1;
-    private Stack<Integer> s2;
-    
+    private Deque<Integer> s1;
+    private Deque<Integer> s2;
+
     /** initialize your data structure here. */
     public MinStack() {
-        s1 = new Stack<>();
-        s2 = new Stack<>();
+        s1 = new ArrayDeque<>();
+        s2 = new ArrayDeque<>();
     }
 
     public void push(int x) {
         s1.push(x);
-        s2.push((s2.empty() || s2.peek() > x) ? x : s2.peek());
+        s2.push(s2.isEmpty() || s2.peek() >= x ? x : s2.peek());
     }
 
     public void pop() {

lcof/面试题30. 包含min函数的栈/Solution.py

@@ -4,22 +4,22 @@ def __init__(self):
         """
         initialize your data structure here.
         """
-        self._s1 = []
-        self._s2 = []
+        self.s1 = []
+        self.s2 = []
 
     def push(self, x: int) -> None:
-        self._s1.append(x)
-        self._s2.append(x if len(self._s2) == 0 or self._s2[-1] > x else self._s2[-1])
+        self.s1.append(x)
+        self.s2.append(x if not self.s2 or self.s2[-1] >= x else self.s2[-1])
 
     def pop(self) -> None:
-        self._s1.pop()
-        self._s2.pop()
+        self.s1.pop()
+        self.s2.pop()
 
     def top(self) -> int:
-        return self._s1[-1]
+        return self.s1[-1]
 
     def min(self) -> int:
-        return self._s2[-1]
+        return self.s2[-1]
 
 
 # Your MinStack object will be instantiated and called as such:

lcof/面试题31. 栈的压入、弹出序列/README.md

@@ -45,16 +45,14 @@ push(5), pop() -> 5, pop() -> 3, pop() -> 2, pop() -> 1
 ```python
 class Solution:
     def validateStackSequences(self, pushed: List[int], popped: List[int]) -> bool:
-        t = []
-        for num in popped:
-            while len(t) == 0 or t[-1] != num:
-                if len(pushed) == 0:
-                    return False
-                t.append(pushed[0])
-                pushed = pushed[1:]
-            t.pop()
-        return True
-
+        s = []
+        q = 0
+        for num in pushed:
+            s.append(num)
+            while s and s[-1] == popped[q]:
+                s.pop()
+                q += 1
+        return not s
 ```
 
 ### **Java**
@@ -64,18 +62,16 @@ class Solution:
 ```java
 class Solution {
     public boolean validateStackSequences(int[] pushed, int[] popped) {
-        Stack<Integer> t = new Stack<>();
-        int i = 0, n = pushed.length;
-        for (int num : popped) {
-            while (t.empty() || t.peek() != num) {
-                if (i == n) {
-                    return false;
-                }
-                t.push(pushed[i++]);
+        Deque<Integer> s = new ArrayDeque<>();
+        int q = 0;
+        for (int num : pushed) {
+            s.push(num);
+            while (!s.isEmpty() && s.peek() == popped[q]) {
+                s.pop();
+                ++q;
             }
-            t.pop();
         }
-        return true;
+        return s.isEmpty();
     }
 }
 ```
@@ -88,25 +84,17 @@ class Solution {
  * @param {number[]} popped
  * @return {boolean}
  */
-var validateStackSequences = function (pushed, popped) {
-  let stack = [];
-  while (pushed.length && popped.length) {
-    if (pushed[0] === popped[0]) {
-      pushed.shift();
-      popped.shift();
-    } else if (popped[0] === stack[0]) {
-      stack.shift();
-      popped.shift();
-    } else {
-      stack.unshift(pushed.shift());
+var validateStackSequences = function(pushed, popped) {
+    let s = [];
+    let q = 0;
+    for (let num of pushed) {
+        s.push(num);
+        while (s.length > 0 && s[s.length - 1] == popped[q]) {
+            ++q;
+            s.pop();
+        }
     }
-  }
-  while (stack.length) {
-    if (stack[0] !== popped[0]) return false;
-    stack.shift();
-    popped.shift();
-  }
-  return true;
+    return s.length == 0;
 };
 ```
 

lcof/面试题31. 栈的压入、弹出序列/Solution.java

@@ -1,16 +1,14 @@
 class Solution {
     public boolean validateStackSequences(int[] pushed, int[] popped) {
-        Stack<Integer> t = new Stack<>();
-        int i = 0, n = pushed.length;
-        for (int num : popped) {
-            while (t.empty() || t.peek() != num) {
-                if (i == n) {
-                    return false;
-                }
-                t.push(pushed[i++]);
+        Deque<Integer> s = new ArrayDeque<>();
+        int q = 0;
+        for (int num : pushed) {
+            s.push(num);
+            while (!s.isEmpty() && s.peek() == popped[q]) {
+                s.pop();
+                ++q;
             }
-            t.pop();
         }
-        return true;
+        return s.isEmpty();
     }
 }

lcof/面试题31. 栈的压入、弹出序列/Solution.js

@@ -3,23 +3,15 @@
  * @param {number[]} popped
  * @return {boolean}
  */
-var validateStackSequences = function (pushed, popped) {
-  let stack = [];
-  while (pushed.length && popped.length) {
-    if (pushed[0] === popped[0]) {
-      pushed.shift();
-      popped.shift();
-    } else if (popped[0] === stack[0]) {
-      stack.shift();
-      popped.shift();
-    } else {
-      stack.unshift(pushed.shift());
-    }
+var validateStackSequences = function(pushed, popped) {
+  let s = [];
+  let q = 0;
+  for (let num of pushed) {
+      s.push(num);
+      while (s.length > 0 && s[s.length - 1] == popped[q]) {
+          ++q;
+          s.pop();
+      }
   }
-  while (stack.length) {
-    if (stack[0] !== popped[0]) return false;
-    stack.shift();
-    popped.shift();
-  }
-  return true;
-};
+  return s.length == 0;
+};

lcof/面试题31. 栈的压入、弹出序列/Solution.py

@@ -1,12 +1,10 @@
 class Solution:
-    def validateStackSequences(self, pushed: List[int],
-                               popped: List[int]) -> bool:
-        t = []
-        for num in popped:
-            while len(t) == 0 or t[-1] != num:
-                if len(pushed) == 0:
-                    return False
-                t.append(pushed[0])
-                pushed = pushed[1:]
-            t.pop()
-        return True
+    def validateStackSequences(self, pushed: List[int], popped: List[int]) -> bool:
+        s = []
+        q = 0
+        for num in pushed:
+            s.append(num)
+            while s and s[-1] == popped[q]:
+                s.pop()
+                q += 1
+        return not s