Class Solution
Medium
You are given two positive integers startPos
and endPos
. Initially, you are standing at position startPos
on an infinite number line. With one step, you can move either one position to the left, or one position to the right.
Given a positive integer k
, return the number of different ways to reach the position endPos
starting from startPos
, such that you perform exactly k
steps. Since the answer may be very large, return it modulo 109 + 7
.
Two ways are considered different if the order of the steps made is not exactly the same.
Note that the number line includes negative integers.
Example 1:
Input: startPos = 1, endPos = 2, k = 3
Output: 3
Explanation: We can reach position 2 from 1 in exactly 3 steps in three ways:
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1 -> 2 -> 3 -> 2.
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1 -> 2 -> 1 -> 2.
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1 -> 0 -> 1 -> 2.
It can be proven that no other way is possible, so we return 3.
Example 2:
Input: startPos = 2, endPos = 5, k = 10
Output: 0
Explanation: It is impossible to reach position 5 from position 2 in exactly 10 steps.
Constraints:
1 <= startPos, endPos, k <= 1000
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Constructor Summary
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Method Summary
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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Constructor Details
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Solution
public Solution()
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Method Details
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numberOfWays
public int numberOfWays(int startPos, int endPos, int k)
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