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Program.cs
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Program.cs
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//创建res数组接收结果,长度为2,初始值设为-1。创建left和right指针指向数组头和尾。
//在left <= right的条件下遍历数组,如果res的两个元素分别为left和right的时候停止遍历。
//如果left指向的元素与target相等就将left存入res,否则让left向右移动一位(由于数组是排好序的,如果当前left指向的元素不等于target,则只有向右移才有可能找到target)。
//如果right指向元素与target相等就将right存入res,否则让right向左移动一位(理由同上)。
//最后返回res
using System;
namespace FindFirstAndLastPositionOfElement
{
class Program
{
static void Main(string[] args)
{
int[] nums = { 5, 7, 7, 8, 8, 10 };
int target = 8;
Console.WriteLine(SearchRange(nums, target));
}
static int[] SearchRange(int[] nums, int target)
{
int[] res = { -1, -1 };
int left = 0;
int right = nums.Length - 1;
while (left <= right)
{
if (res[0] == left && res[1] == right)
break;
if (nums[left] == target)
res[0] = left;
else
left++;
if (nums[right] == target)
res[1] = right;
else
right--;
}
return res;
}
static int[] SearchRange_BinarySearch(int[] nums, int target)
{
int[] res = { -1, -1 };
int li = 0, hi = nums.Length - 1;
while (li <= hi)
{
int mid = li + (hi - li) / 2;
if (nums[mid] < target)
li = mid + 1;
else
hi = mid - 1;
}
if (hi + 1 <= nums.Length - 1 && nums[hi + 1] == target)
res[0] = hi + 1;
li = 0;
hi = nums.Length - 1;
while (li <= hi)
{
int mid = li + (hi - li) / 2;
if (nums[mid] <= target)
li = mid + 1;
else
hi = mid - 1;
}
if (li - 1 >= 0 && nums[li - 1] == target)
res[1] = li - 1;
return res;
}
}
}