Changes made by akruti, added a new python leetcode problem

Python/PermutationSequence.py

@@ -0,0 +1,35 @@
+#Problem link - https://leetcode.com/problems/permutation-sequence/
+class Solution(object):
+    def getPermutation(self, n, k):
+        """
+        :type n: int
+        :type k: int
+        :rtype: str
+        """
+        # let permutations with first identical num be a block
+        # target in (k - 1) / (n - 1)! block
+        remain = range(1, n + 1)
+        if k <= 1:
+            return ''.join(str(t) for t in remain)
+        total = 1
+        for num in remain[:-1]:
+            total *= num
+        res = self.do_getPermutation(remain, total, n - 1, k - 1)
+        return ''.join(str(t) for t in res)
+
+
+    def do_getPermutation(self, remain, curr, n, k):
+        if n == 0 or k <= 0 or curr == 0:
+            return remain
+        # which block
+        step = k / curr
+        # remain k value
+        k %= curr
+        curr /= n
+        res = [remain[step]] + self.do_getPermutation(remain[:step] + remain[step + 1:], curr, n - 1, k)
+        return res
+
+if __name__ == '__main__':
+    s = Solution()
+    print s.getPermutation(3, 2)
+    # print s.getPermutation(2, 2)