Solution 1 for Scaler Topics Fortnightly Contest - 15

This article is part of the Scaler Topics Fortnightly Contest - 15

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Solution Approach

• First we could find the xor of the lost pair, this would be equal to the xor of all the elements xorred with xor of remaining elements.
• Initially, we had xorred with the xor of remaining elements which is B.
• Then iterate for all integers in range [1, A] and check for every integer,
• if there exist any other integer in the range [1, A] such that the xor of these two is equal to the xor of the lost pair,
• for checking this let X be the integer for which we are checking then we want element with xor equal to the xor of X and the xor of remaining elements which we found out initially.
• And also we have counted every pair twice so divide the result by two.

C++ Implementation

Java Implementation

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Python Implementation