43 lines
1.3 KiB
Ruby
43 lines
1.3 KiB
Ruby
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# There are 2 sorted arrays A and B of size n each.
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# find the median of the array obtained after merging the above 2 arrays(i.e. array of length 2n).
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#Algorithm :Binary-search
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#Time-complexity:O(logn),Auxiliary-space: O(1)
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def get_median(a,a1,lo1,hi1,lo2,hi2)
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#Length of the arrays
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len=hi1-lo1+1
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return -1 if len<=0 # return -1 if array is empty or invalid
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return (a[lo1]+a1[lo2])/2 if len==1 # return median if each array is of size 1
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return ([a[lo1], a1[lo2]].max + [a[hi1], a1[hi2]].min)/2 if len==2 # return median if each array is of size 2
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#Median and index of median of array 1
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m1,m1_i=median(a,len,lo1)
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#Median and index of median of array 2
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m2,m2_i=median(a1,len,lo2)
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#Compare medians if equal return either m1 or m2,
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#else if m1<m2 median lies in m1,hi1 and lo1,m2
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#else m1>m2 median lies in m1,hi1 and lo1,m2
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if m1==m2
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return m1
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elsif m1<m2
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return get_median(a,a1,m1_i,hi1,lo2,m2_i)
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else
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return get_median(a,a1,lo1,m1_i,m2_i,hi2)
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end
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end
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# Utility function to find median of array
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def median(arr,n,lo)
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if n%2==0
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return (arr[lo+(n/2)]+arr[lo+((n/2)-1)])/2,lo+(n/2)
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else
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return arr[lo+(n/2)],lo+(n/2)
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end
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end
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get_median([1,2,3,5,5],[1,2,5,9,11],0,4,0,4) # => 4
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