找出给定整数在一个有序数组中的区间。
比如，对于数组“1，3，5，7，10”，给定“2”，找到它在“3”和“5”区间内。要求用二分搜索。时间控制在log2n内。
using System;using System.Collections.Generic;using System.Linq;using System.Text;namespace ConsoleApplication3{ class Program { static void Main(string[] args) { int[] a = new int[] { 1, 3, 5, 7, 10, 11, 13, 15, 17 }; for (int i = 1; i <= 17; ++i) { int left = -1; int right = -1; biSearch(a, i, out left, out right); int l = -1; int r = -1; sequenceSearch(a, i, out l, out r); Console.WriteLine(string.Format("Search {0}, Index: {1}-{2}, Value: {3}-{4}, TestResult: {5}", i, left, right, a[left], a[right], left == l && right == r)); } } static bool biSearch(int[] a, int t, out int left, out int right) { left = -1; right = a.Length; int n = a.Length; int l = 0; int b = n - 1; int m = -1; while (l <= b) { m = (l + b) / 2; if (a[m] < t) { l = m + 1; left = m; } else if (a[m] == t) { left = m; right = m; return true; } else //a[m] > t { b = m - 1; right = m; } } return left >= 0 && right < a.Length; } static bool sequenceSearch(int[] a, int t, out int right, out int left) { right = -1; left = a.Length; for (int i = 0; i < a.Length; ++i) { if (a[i] < t) { right = i; } else if (a[i] > t) { left = i; return right >= 0; } else //a[i]==i { left = i; right = i; return true; } } return left < a.Length; } }}