Search in a sorted rotated array

Question: Implement a search function for a sorted rotated array. Duplicates are allowed. Returning any one of the duplicates is acceptable.
Answer: We can do a binary search with some modified checks.
public int rotatedSearch(int[] values, int start, int end, 
                          int x){
    if(values[start] == x){
        return start;
    } else if(values[end] == x){
        return end;
    } else if(end - start == 1) {
        return -1;
    }
    int middle = (start + end) / 2;

    if(values[start] <= values[middle]){
        if(x <= values[middle] && x >= values[start]){
            return rotatedSearch(values, start, middle, x);
        } else {
            return rotatedSearch(values, middle, end, x);
        }
    } else if(values[middle] <= values[end]){
        if(x >= values[middle] && x <= values[end] ){
            return rotatedSearch(values, middle, end, x);
        } else {
            return rotatedSearch(values, start, middle, x);
        }
    } else {
        return -1;
    }
}

Comments

Post a Comment

Popular posts from this blog

Pick a Random Byte

Question:  You have a stream of bytes from which you can read one byte at a time. You only have enough space to store one byte. After processing those bytes, you have to return a random byte. Note: The probability of picking any one of those bytes should be equal. Answer:  Since we can only store one byte at a time, we have to be able to work with the bytes as they come in. We can’t store everything, count the number of bytes and pick one. That would be too easy wouldn’t it? Let’s think it through. We don’t know how many bytes there are, so at any point in time we should have a random byte picked from all the bytes we have seen so far. We shouldn’t worry about the total number of bytes at any time. When we get the first byte, it is simple. There is only one so we store it. When we get the second one, it has 1/2 probability of being picked and the one we have stored has a 1/2 probability of being picked (we can use any programming language’s built-in random functio...
Read more

Singly Linked List – Delete Node

Question:  You are given a pointer to a node (not the tail node) in a singly linked list. Delete that node from the linked list. Write code in C. Answer:  To delete a node, you have to redirect the next pointer of the previous node to point to the next node instead of the current one. Since we don’t have a pointer to the previous node, we can’t redirect its next pointer. So what do we do? We can easily get away by moving the data from the next node into the current node and then deleting the next node.  This solution has O(1) runtime. Here’s some code to illustrate this simple logic. void deleteNode( Node * node ) { Node * temp = node->next; node->data = node->next->data; node->next = temp->next; free(temp); } Some things to consider. This method could pose potential problems. For instance, let’s consider we have a linked list A -> B -> C -> D and we are given a pointer to B to delete it. Theoretical...
Read more