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14c314c08c
* Retranslate the complete English edition from Simplified Chinese * Polish three English explanations after reader-focused review
61 lines
2.1 KiB
JavaScript
61 lines
2.1 KiB
JavaScript
/**
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* File: binary_search.js
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* Created Time: 2022-12-22
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* Author: JoseHung (szhong@link.cuhk.edu.hk)
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*/
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/* Binary search (closed interval) */
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function binarySearch(nums, target) {
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// Initialize the closed interval [0, n-1], with i and j pointing to the first and last elements
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let i = 0,
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j = nums.length - 1;
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// Loop until the search interval is empty (when i > j)
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while (i <= j) {
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// Calculate midpoint index m, using parseInt() to round down
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const m = parseInt(i + (j - i) / 2);
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if (nums[m] < target)
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// In this case, target must be in [m+1, j] if it exists
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i = m + 1;
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else if (nums[m] > target)
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// In this case, target must be in [i, m-1] if it exists
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j = m - 1;
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else return m; // The target element was found; return its index
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}
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// The target element was not found; return -1
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return -1;
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}
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/* Binary search (left-closed, right-open interval) */
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function binarySearchLCRO(nums, target) {
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// Initialize the left-closed, right-open interval [0, n), with i at the first element and j one past the last
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let i = 0,
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j = nums.length;
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// Loop until the search interval is empty (when i = j)
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while (i < j) {
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// Calculate midpoint index m, using parseInt() to round down
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const m = parseInt(i + (j - i) / 2);
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if (nums[m] < target)
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// In this case, target must be in [m+1, j) if it exists
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i = m + 1;
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else if (nums[m] > target)
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// In this case, target must be in [i, m) if it exists
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j = m;
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// The target element was found; return its index
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else return m;
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}
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// The target element was not found; return -1
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return -1;
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}
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/* Driver code */
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const target = 6;
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const nums = [1, 3, 6, 8, 12, 15, 23, 26, 31, 35];
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/* Binary search (closed interval) */
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let index = binarySearch(nums, target);
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console.log('Index of target element 6 = ' + index);
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/* Binary search (left-closed, right-open interval) */
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index = binarySearchLCRO(nums, target);
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console.log('Index of target element 6 = ' + index);
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