What is the default scope of spring beans? how to change it? What is dependency injection? How does garbage collection work in java? Future class in java? flip 1s to 2s without conditional statements? bottom view of a binary tree?

1st Round: 3 coding questions moderate level (time =2 hours)..dont remember the questions exactly ..one of them was based on stack(next greater and next smaller type question) and other one was on dfs/bfs. ones who solved one question got into 2nd round. 14/180 qualified for 2nd round. 2nd round: It was interview face to face. He asked me 3 coding questions.. 1: given a knight and a position on chessboard..will knight reach that position ever? 2:given some playing cards one of them is missing..you have to find which one is missing 3: dont remember exactly i answered all of them 3rd round: 3 coding questions: 1: given an array of 1's and 0 's find maximum subarray length whose no of 1's==no of 0's 2:you have very large strings and there is stream of them you have to find if it has come before or not? 3:dont remember exactly