65 lines
2.5 KiB
C#
65 lines
2.5 KiB
C#
/**
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* File: binary_search_insertion.cs
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* Created Time: 2023-08-06
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* Author: hpstory (hpstory1024@163.com)
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*/
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namespace hello_algo.chapter_searching;
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public class binary_search_insertion {
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/* Binary search for insertion point (no duplicate elements) */
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public static int BinarySearchInsertionSimple(int[] nums, int target) {
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int i = 0, j = nums.Length - 1; // Initialize double closed interval [0, n-1]
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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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i = m + 1; // Target is in interval [m+1, j]
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} else if (nums[m] > target) {
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j = m - 1; // Target is in interval [i, m-1]
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} else {
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return m; // Found target, return insertion point m
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}
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}
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// Did not find target, return insertion point i
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return i;
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}
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/* Binary search for insertion point (with duplicate elements) */
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public static int BinarySearchInsertion(int[] nums, int target) {
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int i = 0, j = nums.Length - 1; // Initialize double closed interval [0, n-1]
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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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i = m + 1; // Target is in interval [m+1, j]
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} else if (nums[m] > target) {
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j = m - 1; // Target is in interval [i, m-1]
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} else {
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j = m - 1; // First element less than target is in interval [i, m-1]
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}
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}
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// Return insertion point i
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return i;
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}
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[Test]
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public void Test() {
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// Array without duplicate elements
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int[] nums = [1, 3, 6, 8, 12, 15, 23, 26, 31, 35];
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Console.WriteLine("\nArray nums =" + nums.PrintList());
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// Binary search for insertion point
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foreach (int target in new int[] { 6, 9 }) {
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int index = BinarySearchInsertionSimple(nums, target);
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Console.WriteLine("The insertion point index for element " + target + " is" + index);
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}
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// Array with duplicate elements
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nums = [1, 3, 6, 6, 6, 6, 6, 10, 12, 15];
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Console.WriteLine("\nArray nums =" + nums.PrintList());
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// Binary search for insertion point
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foreach (int target in new int[] { 2, 6, 20 }) {
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int index = BinarySearchInsertion(nums, target);
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Console.WriteLine("The insertion point index for element " + target + " is" + index);
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}
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}
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}
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