检查号码列表是否连续

Question

I have quite a layman question about Java programming.

I would like to write a function to check whether a list of number is sequential or not.

Say [1, 2, 3, 4, 5], the function will return true,

but for [1, 3, 4, 9, 10], the function will return false.

Could anyone help me?

Thank so much!

Answer 1

Write a loop that looks at each element of the list.

For each position i in the list, test that list _i + 1 equals list _{i + 1} .

You can code it yourself as an exercise. (Don't forget to deal with the edge cases ...)

---

UPDATE: ... for people treating this problem as a learning exercise.

A simple direct implementation approach is probably the best idea; eg @Joe's final answer. However, the simple approach doesn't always work well ... or at all:

• Some Java List implementations have a get method that is O(N) . That would lead to an O(N^2) algorithm overall.
• Sometimes aa list can only be accessed using an iterator; ie list.get(i) might not be an option.

In such cases, you could implement the algorithm with one pass through the list using an iterator. You need to keep "the previous element" in variable, etcetera.

Answer 2

Logic is simple. Just get the first number and check whether it matches with the next value. Like that check adjacent values. Break if the condition fails at any point. The list will be sequential if all the if condition is true.

Answer 3

As Stephen C said, it is a very simple logic

int a[] = { 1, 2, 3, 4, 5,7 };
        boolean flag = true;
        for (int i = 0; i < a.length - 1; i++) {
            if (a[i + 1] != a[i] + 1) {
                flag = false;
                break;

            }
        }
        System.out.println("Flag is " + flag);