52 lines
1.6 KiB
Swift
52 lines
1.6 KiB
Swift
/**
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* File: binary_search_edge.swift
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* Created Time: 2023-08-06
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* Author: nuomi1 (nuomi1@qq.com)
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*/
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import binary_search_insertion_target
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/* Binary search for the leftmost target */
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func binarySearchLeftEdge(nums: [Int], target: Int) -> Int {
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// Equivalent to finding the insertion point of target
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let i = binarySearchInsertion(nums: nums, target: target)
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// Did not find target, thus return -1
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if i == nums.endIndex || nums[i] != target {
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return -1
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}
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// Found target, return index i
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return i
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}
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/* Binary search for the rightmost target */
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func binarySearchRightEdge(nums: [Int], target: Int) -> Int {
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// Convert to finding the leftmost target + 1
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let i = binarySearchInsertion(nums: nums, target: target + 1)
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// j points to the rightmost target, i points to the first element greater than target
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let j = i - 1
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// Did not find target, thus return -1
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if j == -1 || nums[j] != target {
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return -1
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}
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// Found target, return index j
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return j
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}
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@main
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enum BinarySearchEdge {
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/* Driver Code */
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static func main() {
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// Array with duplicate elements
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let nums = [1, 3, 6, 6, 6, 6, 6, 10, 12, 15]
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print("\nArray nums = \(nums)")
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// Binary search for left and right boundaries
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for target in [6, 7] {
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var index = binarySearchLeftEdge(nums: nums, target: target)
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print("The leftmost index of element \(target) is \(index)")
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index = binarySearchRightEdge(nums: nums, target: target)
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print("The rightmost index of element \(target) is \(index)")
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}
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}
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}
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