Create 0041_findingLeastPositiveNumber.py

LeetCode/0041_findingLeastPositiveNumber.py

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+# finding least positive number
+# Given an array of integers, find the first missing positive integer in linear time and constant space. In other words,
+# find the lowest positive integer that does not exist in the array. The array can contain duplicates and negative numbers as well.
+# code contributed by devanshi katyal
+# space complexity:O(1)
+# time complexity:O(n)
+
+
+def MainFunction(arr, size):
+ for i in range(size):
+ if (abs(arr[i]) - 1 < size and arr[abs(arr[i]) - 1] > 0):
+ arr[abs(arr[i]) - 1] = -arr[abs(arr[i]) - 1]
+ for i in range(size):
+ if (arr[i] > 0):
+ return i + 1
+ return size + 1
+
+def findpositive(arr, size):
+ j= 0
+ for i in range(size):
+ if (arr[i] <= 0):
+ arr[i], arr[j] = arr[j], arr[i]
+ j += 1
+ return MainFunction(arr[j:], size - j)
+arr = list(map(int, input().split(" ")))
+print("the smallest missing number", findpositive(arr, len(arr)))