{ "data": { "question": { "questionId": "1684", "questionFrontendId": "1562", "boundTopicId": null, "title": "Find Latest Group of Size M", "titleSlug": "find-latest-group-of-size-m", "content": "

Given an array arr that represents a permutation of numbers from 1 to n.

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You have a binary string of size n that initially has all its bits set to zero. At each step i (assuming both the binary string and arr are 1-indexed) from 1 to n, the bit at position arr[i] is set to 1.

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You are also given an integer m. Find the latest step at which there exists a group of ones of length m. A group of ones is a contiguous substring of 1's such that it cannot be extended in either direction.

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Return the latest step at which there exists a group of ones of length exactly m. If no such group exists, return -1.

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Example 1:

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\nInput: arr = [3,5,1,2,4], m = 1\nOutput: 4\nExplanation: \nStep 1: "00100", groups: ["1"]\nStep 2: "00101", groups: ["1", "1"]\nStep 3: "10101", groups: ["1", "1", "1"]\nStep 4: "11101", groups: ["111", "1"]\nStep 5: "11111", groups: ["11111"]\nThe latest step at which there exists a group of size 1 is step 4.\n
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Example 2:

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\nInput: arr = [3,1,5,4,2], m = 2\nOutput: -1\nExplanation: \nStep 1: "00100", groups: ["1"]\nStep 2: "10100", groups: ["1", "1"]\nStep 3: "10101", groups: ["1", "1", "1"]\nStep 4: "10111", groups: ["1", "111"]\nStep 5: "11111", groups: ["11111"]\nNo group of size 2 exists during any step.\n
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Constraints:

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