Given two positive integers X and Y, and an array arr of positive integers. We need to find the longest prefix index which contains an equal number of X and Y. Print the maximum index of largest prefix if exist otherwise print -1.
Input : array = [7, 42, 5, 6, 42, 8, 7, 5, 3, 6, 7] X = 7 Y = 42 Output : 9 The longest prefix with same number of occurrences of 7 and 42 is: 7, 42, 5, 6, 42, 8, 7, 5, 3, 6 42
We start from the index 0 and run a loop till the end of array. We keep increasing counters for both numbers X and Y. After iterating over the whole array, the last index when counts of X and y were equal is our result.
Below is the implementation of above idea :
Ending index of prefix is 9
Time complexity : O(n)
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