Create FirstMissingPositive.py

Author: CHALLANIKITHA

Diff for: python/FirstMissingPositive.py

@@ -0,0 +1,22 @@
+"""
+https://leetcode.com/problems/first-missing-positive/
+Given an unsorted integer array nums, return the smallest missing positive integer.
+"""
+class Solution(object):
+    def firstMissingPositive(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: int
+        """
+        i=0
+        while i<len(nums):
+            correct=nums[i]-1
+            if nums[i]>0 and correct<len(nums) and  nums[i]!=nums[correct]:
+                     nums[i],nums[correct]=nums[correct],nums[i]
+            else:
+                i+=1
+        flag=0
+        for j in range(0,len(nums)):
+            if nums[j]-1!=j:
+                return j+1
+        return len(nums)+1