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55 lines
1.1 KiB
Ruby
55 lines
1.1 KiB
Ruby
# Given a sorted array of n unique integers where each integer is in the range from 0 to m-1 and m > n.
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# Find the smallest number that is missing from the array.
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#Algorithm: Binary Search (Compare elements with indexes and then decide)
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#Time-complexity: O(logn), Auxiliary-space: O(1)
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# Iterative
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def smallest_missing(a)
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lo=0
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hi=a.length-1
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while hi>lo
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mid=lo+(hi-lo)/2
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if a[mid]>mid
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hi=mid
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else
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lo=mid+1
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end
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end
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if a[lo]==lo # if lo == end of array
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print lo+1
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else
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print lo
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end
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end
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smallest_missing([0, 1, 2, 3]) #=> 4
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smallest_missing([0, 1, 2, 5]) #=> 3
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#recursive
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#Driver function
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def driver_func(a)
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lo=0
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hi=a.length-1
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print smallest_missing(a,lo,hi)
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end
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#Algorithm
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def smallest_missing(a,lo,hi)
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if lo>hi
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return hi+1
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end
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if a[lo] != lo
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return lo
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end
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mid= lo+(hi-lo)/2
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if a[mid]>mid
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return smallest_missing(a,lo,mid)
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else
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return smallest_missing(a,mid+1,hi)
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end
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end
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driver_func([0, 1, 2, 3]) #=> 4
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driver_func([0, 1, 2, 5]) #=> 3
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