Given two arrays a and b, we need to build an array c such that every element c[i] of c contains a value from a which is greater than b[i] and is closest to b[i]. If a has no greater element than b[i], then value of c[i] is -1. All arrays are of same size.
Input : a = [ 2, 6, 5, 7, 0] b = [1, 3, 2, 5, 8] Output : c = [2, 5, 5, 7, -1] Input : a = [ 2, 6, 5, 7, 0] b = [0, 2, 3, 5, 1] Output : c = [2, 5, 5, 6, 2]
Naive Approach : For each element in b, we traverse the whole of a and try to find the closest greater element, and save the result for each search. This will cost time complexity of O(n^2).
Efficient Approach : Sort the array a, and for each b[i], apply binary search in sorted array a. For this method our time complexity will be O(nlogn).
Note: For closest greater element we can use upper_bound().
Below is the implementation.
Result = 5 2 1 6 5 -1
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Improved By : sanjeev2552