leetcode

Author: springuper

firstMissingPositive.py

@@ -0,0 +1,22 @@
+# @param A, a list of integer
+# @return an integer
+def firstMissingPositive(A):
+    i = 0
+    n = len(A)
+    while i < n:
+        if A[i] != (i + 1) and A[i] > 0 and A[i] <= n and A[i] != A[A[i] - 1]:
+            tmp = A[i]
+            A[i] = A[tmp - 1]
+            A[tmp - 1] = tmp
+        else:
+            i += 1
+
+    for i in range(n):
+        if A[i] != (i + 1):
+            return i + 1
+
+    return n + 1
+
+
+assert firstMissingPositive([1, 2, 0]) == 3
+assert firstMissingPositive([3, 4, -1, 1]) == 2