feat: update solutions to lc problem: No.0050. Pow(x, n)

yanglbme · yanglbme · commit 7fb80c1c3a28 · 2021-06-17T14:22:48.000+08:00
diff --git a/solution/0000-0099/0050.Pow(x, n)/README.md b/solution/0000-0099/0050.Pow(x, n)/README.md
@@ -54,15 +54,35 @@
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```python
-
+class Solution:
+    def myPow(self, x: float, n: int) -> float:
+        if n == 0:
+            return 1
+        if n < 0:
+            return 1 / self.myPow(x, -n)
+        y = self.myPow(x, n >> 1)
+        return y * y if (n & 1) == 0 else y * y * x
 ```
 
 ### **Java**
 
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```java
-
+class Solution {
+    public double myPow(double x, int n) {
+        long N = n;
+        return N >= 0 ? pow(x, N) : 1.0 / pow(x, -N);
+    }
+
+    public double pow(double x, long N) {
+        if (N == 0) {
+            return 1.0;
+        }
+        double y = pow(x, N >> 1);
+        return (N & 1) == 0 ? y * y : y * y * x;
+    }
+}
 ```
 
 ### **...**
diff --git a/solution/0000-0099/0050.Pow(x, n)/README_EN.md b/solution/0000-0099/0050.Pow(x, n)/README_EN.md
@@ -46,13 +46,33 @@
 ### **Python3**
 
 ```python
-
+class Solution:
+    def myPow(self, x: float, n: int) -> float:
+        if n == 0:
+            return 1
+        if n < 0:
+            return 1 / self.myPow(x, -n)
+        y = self.myPow(x, n >> 1)
+        return y * y if (n & 1) == 0 else y * y * x
 ```
 
 ### **Java**
 
 ```java
-
+class Solution {
+    public double myPow(double x, int n) {
+        long N = n;
+        return N >= 0 ? pow(x, N) : 1.0 / pow(x, -N);
+    }
+
+    public double pow(double x, long N) {
+        if (N == 0) {
+            return 1.0;
+        }
+        double y = pow(x, N >> 1);
+        return (N & 1) == 0 ? y * y : y * y * x;
+    }
+}
 ```
 
 ### **...**
diff --git a/solution/0000-0099/0050.Pow(x, n)/Solution.java b/solution/0000-0099/0050.Pow(x, n)/Solution.java
@@ -1,13 +1,14 @@
 class Solution {
     public double myPow(double x, int n) {
-        if(n < 0) return sum(1.0 / x,0 - n);
-        return sum(x,n);
+        long N = n;
+        return N >= 0 ? pow(x, N) : 1.0 / pow(x, -N);
     }
 
-    public double sum(double x, int n) {
-        if(n == 0) return 1;
-        if(n == 1) return x;
-        if( n % 2 == 0) return sum(x * x, n / 2);
-        else return x * sum(x * x, n / 2);
+    public double pow(double x, long N) {
+        if (N == 0) {
+            return 1.0;
+        }
+        double y = pow(x, N >> 1);
+        return (N & 1) == 0 ? y * y : y * y * x;
     }
 }
diff --git a/solution/0000-0099/0050.Pow(x, n)/Solution.py b/solution/0000-0099/0050.Pow(x, n)/Solution.py
@@ -1,21 +1,8 @@
 class Solution:
     def myPow(self, x: float, n: int) -> float:
-        
-        """
-        :type x: float
-        :type n: int
-        :rtype: float
-        """
-        
-        answer = 1
-        if x == 1 or n == 0:
+        if n == 0:
             return 1
-        if x == -1:
-            return 1 if n%2 == 0 else -1
-
-        for i in range(abs(n)):
-            answer *= x
-            if (abs(answer) < 10 ** -5 and n > 0) or (abs(answer) > 10 ** 5 and n < 0):
-                return 0            
-        
-        return answer if n > 0 else 1/answer
+        if n < 0:
+            return 1 / self.myPow(x, -n)
+        y = self.myPow(x, n >> 1)
+        return y * y if (n & 1) == 0 else y * y * x
