1)Relationship for any digit x its value in new number system was 9 - x
2)Converted integer to string
3)Manipulated every index of this string using the relationship.
4)Converted this string to number and returned the answer.

For each node during pre-order traversal of s, use a recursive function isSame to validate if sub-tree started with this node is the same with t.

You can easily observe pattern. It is a Fibonacci sequence 

I thought of two points on a number line a and b and formulated a consecutive sequence [a....b], (b*(b+1))/2-(a*(a+1))/2=n. Now we have a clearly quadratic solution by brute-forcing a and b but if we simplify it further we have (b-a+1)*(b+a) = 2*n. So now we can easily find all divisors of 2*n and satisfy the equation for which we get a>=0 and b>=0 and thus we get the answer.

I knew the recursive solution as it is a very popular interview problem.The idea is much like the insertion sort. We start with only the first number, and pick next number from the rest of array, insert it to the front or back position of the first number, and pick the third number, insert it to front or mid or back position of the [first, second] array, and so on, until no element left.

Easy problem iterate over the longer string and keep a counter for matching it with shorter string if a match occurs while iterating longer string increment the counter and if we have done iterating on the longer string if the counter value is equal to shorter string length then return true else return false.

It was also an easy problem as I had done it before.The minimum path to get to element A[i][j] is the minimum of A[i - 1][j - 1], A[i - 1][j] and A[i - 1][j + 1]. Starting from row 1, we add the minimum path to each element. The smallest number in the last row is the minimum path sum.

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