1345. Jump Game IV
https://leetcode.com/problems/jump-game-iv/
Given an array of integers
arr, you are initially positioned at the first index of the array.
In one step you can jump from index
i to index:i + 1where:i + 1 < arr.length.i - 1where:i - 1 >= 0.jwhere:arr[i] == arr[j]andi != j.
Return the minimum number of steps to reach the last index of the array.
Notice that you can not jump outside of the array at any time.
Example 1:
Input: arr = [100,-23,-23,404,100,23,23,23,3,404] Output: 3 Explanation: You need three jumps from index 0 --> 4 --> 3 --> 9. Note that index 9 is the last index of the array.
Example 2:
Input: arr = [7] Output: 0 Explanation: Start index is the last index. You don't need to jump.
Example 3:
Input: arr = [7,6,9,6,9,6,9,7] Output: 1 Explanation: You can jump directly from index 0 to index 7 which is last index of the array.
Example 4:
Input: arr = [6,1,9] Output: 2
Example 5:
Input: arr = [11,22,7,7,7,7,7,7,7,22,13] Output: 3
Constraints:
1 <= arr.length <= 5 * 10^4-10^8 <= arr[i] <= 10^8
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Intuition
Shortest path => BFS => Queue - Iterative level order traversal
Number of levels = number of steps
neighbors are +1, -1, and equal valued indices
we may check for early termination only for +1, and equal valued indices
-1 cannot be end state, and no need to check early termination for -1
We need one linear pass to map value, and set of indices with equal value
Once we've tested equal valued neighbors, we can remove it from the map since they should be not checked for other neighbors
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Time - O(n)
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