Add Soulution2.java for 0343.Integer Break

solution/0343.Integer Break/README_EN.md

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+# Integer Break
+
+Given a positive integer n, break it into the sum of **at least** two positive integers and maximize the product of those integers. Return the maximum product you can get.
+
+## Example 1:
+```
+ Input: 2
+ Output: 1
+ Explanation: 2 = 1 + 1, 1 × 1 = 1.
+```
+
+## Example 2:
+```
+ Input: 10
+  Output: 36
+  Explanation: 10 = 3 + 3 + 4, 3 × 3 × 4 = 36.
+```
+Note: You may assume that n is not less than 2 and not larger than 58.

solution/0343.Integer Break/Solution2.java

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+/**
+ * O(1) ==》 time complexity
+ * O(1) ==》space complexity
+ */
+class Solution {
+    public int integerBreak(int n) {
+        if (n <= 3) return n-1;
+
+        int a = n/3, b = n%3;
+        if (b == 0) return pow(3, a);
+        if (b == 1) return pow(3, a-1) << 2;
+        return pow(3, a) << 1;
+    }
+
+    private int pow(int a, int b) {
+        if (b == 0) return 1;
+        return a * pow(a,  b-1);
+    }
+}