LeetCode算法题

/// <summary>

/// 两数之和

/// </summary>

/// <param name="nums"></param>

/// <param name="target"></param>

/// <returns></returns>

public static int[] TwoSum(int[] nums, int target)

{

    for (int i = 0; i < nums.Length; i++)

    {

        for (int j = 0; j < nums.Length; j++)

        {

            if (i != j)

            {

                if (nums[i] + nums[j] == target)

                {

                    return new int[] { i, j };

                }

            }

        }

    }

    return null;

}

public class ListNode

{

    public int val;

    public ListNode next;

    public ListNode(int val = 0, ListNode next = null)

    {

        this.val = val;

        this.next = next;

    }

}

/// <summary>

/// 两数相加（抄来的并且已经提交）

/// </summary>

/// <param name="l1"></param>

/// <param name="l2"></param>

/// <returns></returns>

public static ListNode AddTwoNumbers(ListNode l1, ListNode l2)

{

    ListNode dummyHead = new ListNode(-1);

    ListNode pre = dummyHead;

    int t = 0;

    while (l1 != null || l2 != null || t != 0)

    {

        if (l1 != null)

        {

            t += l1.val;

            l1 = l1.next;

        }

        if (l2 != null)

        {

            t += l2.val;

            l2 = l2.next;

        }

        pre.next = new ListNode(t % 10);

        pre = pre.next;

        t /= 10;

    }

    return dummyHead.next;

}

/// <summary>

/// 回文数

/// </summary>

/// <param name="x"></param>

/// <returns></returns>

public static bool IsPalindrome(int x)

{

    if (x < 0)

    {

        return false;

    }

    string num = x.ToString();

    List<string> list = new List<string>();

    for (int i = 0; i < num.Length; i++)

    {

        list.Add(num[i].ToString());

    }

    var arr = list.ToArray();

    Array.Reverse(arr);

    string num2 = string.Empty;

    for (int i = 0; i < arr.Length; i++)

    {

        num2 += arr[i].ToString();

    }

    return x == Convert.ToInt32(num2);

    // 别人的方法

    //if (x < 0)

    //    return false;

    //int rem = 0, y = 0;

    //int quo = x;

    //while (quo != 0)

    //{

    //    rem = quo % 10;

    //    y = y * 10 + rem;

    //    quo = quo / 10;

    //}

    //return y == x;

}

/// <summary>

/// 有效的括号

/// </summary>

/// <param name="s"></param>

/// <returns></returns>

public static bool IsValid(string s)

{

    while (s.Contains("()") || s.Contains("{}") || s.Contains("[]"))

    {

        s = s.Replace("()", "").Replace("{}", "").Replace("[]", "");

    }

    return s.Length == 0;

}

/// <summary>

/// 各位相加

/// </summary>

/// <param name="num"></param>

/// <returns></returns>

public static int AddDigits(int num)

{

    string number = num.ToString();

    int x = 0;

    while (Convert.ToInt32(number) >= 10)

    {

       for (int i = 0; i < number.Length; i++)

       {

           x += Convert.ToInt32(number[i].ToString());

       }

       if (x >= 10)

       {

           number = x.ToString();

           x = 0;

           continue;

       }

       return x;

    }

    return num;

    // 别人的方法（属实是佩服这种思路和逻辑）

    //return (num - 1) % 9 + 1;

}

/// <summary>

/// 寻找两个正序数组的中位数

/// </summary>

/// <param name="nums1"></param>

/// <param name="nums2"></param>

/// <returns></returns>

public static double FindMedianSortedArrays(int[] nums1, int[] nums2)

{

    List<int> list = new List<int>();

    list.AddRange(nums1);

    list.AddRange(nums2);

    list.Sort();

    int count = 0;

    if (list.Count % 2 == 0)

    {

        count = list.Count / 2;

        double num = list[count - 1] + list[count];

        return Convert.ToDouble(num / 2);

    }

    list.Add(list[list.Count - 1]);

    list.Sort();

    count = list.Count / 2;

    return list[count - 1];

}

/// <summary>

/// 快乐数

/// </summary>

/// <param name="n"></param>

/// <returns></returns>

public static bool IsHappy(int n)

{

    if (n == 1)

    {

        return true;

    }

    List<int> list = new List<int>();// 存一个数

    while (n > 1)

    {

        int num2 = 0;

        string num = n.ToString();

        for (int i = 0; i < num.Length; i++)

        {

            num2 += Convert.ToInt32(num[i].ToString()) * Convert.ToInt32(num[i].ToString());

        }

        list.Add(num2);

        if (list.Where(s => s.Equals(num2)).ToList().Count > 1)

        {

            // 如果多次循环则返回 false

            return false;

        }

        if (num2 == 1)

        {

            return true;

        }

        n = num2;

    }

    return false;

}

/// <summary>

/// 加一

/// </summary>

/// <param name="digits"></param>

/// <returns></returns>

public static int[] PlusOne(int[] digits)

{

    List<int> list = new List<int>();

    list.AddRange(digits);

    for (int i = digits.Length - 1; i >= 0; i--)

    {

        if (digits[i] != 9)

        {

            // 第一次循环最后一位数不为 9 直接 + 1 返回结果

            digits[i]++;

            return digits;

        }

        // 否则当前下标数进位满 10 为 0

        digits[i] = 0;

    }

    // 循环走完说明全是 9，长度 + 1

    int[] arr = new int[digits.Length + 1];

    arr[0] = 1;

    return arr;

}

/// <summary>

/// 移动零

/// </summary>

/// <param name="nums"></param>

public static void MoveZeroes(int[] nums)

{

    int length = nums.Length;

    int i, j = 0;

    for (i = 0; i < length; i++)

    {

        if (nums[i] != 0)

        {

            nums[j] = nums[i];

            j++;

        }

    }

    while (j < length)

    {

        nums[j++] = 0;

    }

}

/// <summary>

/// 将找到的值乘以 2

/// </summary>

/// <param name="nums"></param>

/// <param name="original"></param>

/// <returns></returns>

public static int FindFinalValue(int[] nums, int original)

{

    for (int i = 0; i < nums.Length; i++)

    {

        if (nums[i] == original)

        {

            return FindFinalValue(nums, original *= 2);

        }

    }

    return original;

}

/// <summary>

/// 排列硬币

/// </summary>

/// <param name="n"></param>

/// <returns></returns>

public static int ArrangeCoins(int n)

{

    if (n == 1)

    {

        return 1;

    }

    int count = 0;

    int m = n;

    for (int i = 1; i < m; i++)

    {

        if (n - i >= 0)

        {

            n -= i;

            count++;

            continue;

        }

        return count;

    }

    return count;

}

/// <summary>

/// 两整数相加

/// </summary>

/// <param name="num1"></param>

/// <param name="num2"></param>

/// <returns></returns>

public static int Sum(int num1, int num2)

{

    return num1 + num2;

}

/// <summary>

/// 只出现一次的数字（抄来的未提交）

/// </summary>

/// <param name="nums"></param>

/// <returns></returns>

public static int SingleNumber(int[] nums)

{

   return nums.Aggregate((a, b) => a ^ b);

}

/// <summary>

/// 只出现一次的数字

/// </summary>

/// <param name="nums"></param>

/// <returns></returns>

public static int SingleNumber(int[] nums)

{

    List<int> list = new List<int>();

    list.AddRange(nums);

    for (int i = 0; i < list.Count; i++)

    {

        if (list.Where(s => s == list[i]).ToList().Count == 1)

        {

            return list[i];

        }

    }

    return 0;

}

/// <summary>

///  2 的幂

/// </summary>

/// <param name="n"></param>

/// <returns></returns>

public static bool IsPowerOfTwo(int n)

{

    if (n == 1)

    {

        return true;

    }

    if (n % 2 != 0 || n <= 0)

    {

        return false;

    }

    return IsPowerOfTwo(n / 2);

}