64 lines
2.1 KiB
Dart
64 lines
2.1 KiB
Dart
/**
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* File: binary_search.dart
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* Created Time: 2023-05-12
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* Author: Jefferson (JeffersonHuang77@gmail.com)
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*/
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/* Binary search (double closed interval) */
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int binarySearch(List<int> nums, int target) {
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// Initialize double closed interval [0, n-1], i.e., i, j point to the first element and last element of the array respectively
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int i = 0, j = nums.length - 1;
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// Loop until the search interval is empty (when i > j, it is empty)
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while (i <= j) {
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int m = i + (j - i) ~/ 2; // Calculate midpoint index m
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if (nums[m] < target) {
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// This situation indicates that target is in the interval [m+1, j]
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i = m + 1;
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} else if (nums[m] > target) {
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// This situation indicates that target is in the interval [i, m-1]
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j = m - 1;
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} else {
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// Found the target element, thus return its index
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return m;
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}
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}
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// Did not find the target element, thus 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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int binarySearchLCRO(List<int> nums, int target) {
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// Initialize left closed right open interval [0, n), i.e., i, j point to the first element and the last element +1 of the array respectively
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int i = 0, j = nums.length;
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// Loop until the search interval is empty (when i = j, it is empty)
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while (i < j) {
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int m = i + (j - i) ~/ 2; // Calculate midpoint index m
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if (nums[m] < target) {
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// This situation indicates that target is in the interval [m+1, j)
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i = m + 1;
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} else if (nums[m] > target) {
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// This situation indicates that target is in the interval [i, m)
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j = m;
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} else {
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// Found the target element, thus return its index
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return m;
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}
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}
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// Did not find the target element, thus return -1
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return -1;
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}
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/* Driver Code*/
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void main() {
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int target = 6;
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final nums = [1, 3, 6, 8, 12, 15, 23, 26, 31, 35];
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/* Binary search (closed interval) */
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int index = binarySearch(nums, target);
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print('目标元素 6 的索引 = $index');
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/* Binary search (left closed right open interval) */
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index = binarySearchLCRO(nums, target);
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print('目标元素 6 的索引 = $index');
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}
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