[Julia] Challenge 7 (Unreviewed)

challenge_7/julia/DTCitron/README.md

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+Find The Missing Number
+======
+Idea
+------
+Given a list of numbers from 0 to N-1, your job is to find the missing number. Your program should take in a list of integers and return a single integer (the missing number).
+
+Note: This is a popular interview question. Bloomberg in particular, really likes this question. 
+
+Input
+-----
+* The list of integers will not be sorted
+* Each value in the list will be between 0 and N
+* Each value will only appear once in the list
+* Only one number will be missing
+
+Requirements
+------------
+* You should not sort the list of integers
+* Your solution should use O(1) space and complete in O(N) time
+* O(1) space means that your algorithm should not need to allocate an additional additional array of N elements to solve the problem
+* O(N) times means that your algorithm can not contain nested loops
+
+Notes
+-----
+* The test cases will not be sorted
+* The fact that the values range from 0 to N is important
+
+Example 1
+---------
+Given the list [0,1,2,4], your program should return the number 3
+
+Example 2
+---------
+Given the list [1,2,3], your program should return the 0.
+
+Testing
+------
+Testing for this challenge is fairly straight forward. Simply create a list of
+size N, filled with integers from 0 to N, with one integer missing.
+
+## Implementation
+
+- Call `python main.py` in the `src` directory to demonstrate
+- Works by exploiting the known sum of the first n+1 integers from 0 to n, comparing the sum of the input list with a missing integer to that known sum
+- More on basic functions on arrays in julia: http://docs.julialang.org/en/release-0.4/stdlib/arrays/

challenge_7/julia/DTCitron/src/findmissing.jl

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+function findMissing(l::Array)
+    n = length(l)
+    return Int(n*(n+1)/2) - sum(l)
+end
+
+t1 = [0,1,2,4];
+println( "Input: ", t1)
+println( "Output: ", findMissing(t1))
+t2 = [1,2,3];
+println( "Input: ", t2)
+println( "Output: ", findMissing(t2))
+t3 = [1,3,4,0];
+println( "Input: ", t3)
+println( "Output: ", findMissing(t3))

challenge_7/python/DTCitron/README.md

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+Find The Missing Number
+======
+Idea
+------
+Given a list of numbers from 0 to N-1, your job is to find the missing number. Your program should take in a list of integers and return a single integer (the missing number).
+
+Note: This is a popular interview question. Bloomberg in particular, really likes this question. 
+
+Input
+-----
+* The list of integers will not be sorted
+* Each value in the list will be between 0 and N
+* Each value will only appear once in the list
+* Only one number will be missing
+
+Requirements
+------------
+* You should not sort the list of integers
+* Your solution should use O(1) space and complete in O(N) time
+* O(1) space means that your algorithm should not need to allocate an additional additional array of N elements to solve the problem
+* O(N) times means that your algorithm can not contain nested loops
+
+Notes
+-----
+* The test cases will not be sorted
+* The fact that the values range from 0 to N is important
+
+Example 1
+---------
+Given the list [0,1,2,4], your program should return the number 3
+
+Example 2
+---------
+Given the list [1,2,3], your program should return the 0.
+
+## Implementation
+
+- Call `python main.py` in the `src` directory to demonstrate
+- Works by exploiting the known sum of the first n+1 integers from 0 to n, comparing the sum of the input list with a missing integer to that known sum
+- Requires numpy to perform the sum over the input list

challenge_7/python/DTCitron/src/main.py

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+import numpy as np
+
+def findMissing(l):
+    n = len(l)
+    return n*(n+1)/2 - np.sum(np.array(l))
+
+if __name__=="__main__":
+    t1 = [0,1,2,4];
+    print "Input: ", t1
+    print "Output: ", findMissing(t1)
+    t2 = [1,2,3];
+    print "Input: ", t2
+    print "Output: ", findMissing(t2)
+    t3 = [1,3,4,0];
+    print "Input: ", t3
+    print "Output: ", findMissing(t3)