10+ Infosys Interview Questions and Answers

Calculate the Nth element of a modified Fibonacci series given the first two numbers and N, with the result modulo 10^9 + 7.

• Implement a function to calculate the Nth element of the series using the Fibonacci rule f(x) = f(x - 1) + f(x - 2)

• Return the answer modulo 10^9 + 7 due to the possibility of a very large result

• The series is 1-based indexed, so the first two numbers are at positions 1 and 2 respectively

Sort an array of 0s, 1s, and 2s in linear time complexity.

• Use three pointers to keep track of 0s, 1s, and 2s while traversing the array.

• Swap elements based on the values encountered to sort the array in-place.

• Time complexity of the algorithm should be O(N) where N is the size of the array.

Count distinct pairs in an array whose sum equals a given target.

• Use two pointers approach to iterate through the array and find pairs with sum equal to target.

• Keep track of visited pairs to avoid counting duplicates.

• Return -1 if no such pair exists with the given target.

Rearrange array to move zeros to the left while maintaining relative order of non-zero elements.

• Iterate through the array and maintain two pointers, one for zero elements and one for non-zero elements.

• Swap elements at the two pointers until all zeros are moved to the left.

• Ensure to maintain the relative order of non-zero elements while rearranging the array.

Find the sum of the subarray with the maximum sum among all subarrays in an array of integers.

• Iterate through the array and keep track of the current sum and maximum sum.

• Update the maximum sum whenever a new maximum subarray sum is found.

• Handle cases where all elements are negative or the array is empty.

• Example: For input arr = [-2, 1, -3, 4, -1], the maximum subarray sum is 4.

Detect and remove loop in a singly linked list in place with O(n) time complexity and O(1) space complexity.

• Use Floyd's Cycle Detection Algorithm to identify the loop in the linked list.

• Once the loop is detected, use two pointers to find the start of the loop.

• Adjust the pointers to remove the loop and return the modified linked list.

Count distinct substrings of a given string using trie data structure.

• Implement a trie data structure to store all substrings of the given string.

• Count the number of nodes in the trie to get the distinct substrings count.

• Handle empty string case separately.

• Example: For 'ab', distinct substrings are: '', 'a', 'b', 'ab'.

Find the equilibrium index of an array where sum of elements on left equals sum on right.

• Iterate through array to calculate prefix and suffix sums

• Compare prefix and suffix sums to find equilibrium index

• Return -1 if no equilibrium index is found

The task is to return the spiral path of elements in a given matrix.

• Iterate through the matrix in a spiral path by adjusting the boundaries of rows and columns.

• Keep track of the direction of traversal (right, down, left, up) to form the spiral path.

• Handle edge cases like when the matrix is a single row or column.

• Implement a function that takes the matrix dimensions and elements as input and returns the spiral path.

The task is to determine the minimum time required to visit all cities and roads in Ninja Land.

• Create a graph representation of the cities and roads.

• Use a traversal algorithm to find the minimum time to visit all cities and roads.

• Return -1 if it is impossible to visit all roads.

• Consider the constraints provided in the problem statement.

• Implement the function to calculate the minimum travel time.