EricWebsmith/Leetcode_csharp

# Notes

Array

Array.Sort(seats); Array.Fill(counts, 1);

Conversion

When converting math formula to from int to long, Convert the first value to long first, So the following computation will be long instead of int. Otherwise, the computation will be int.

Right Way:

long ans = (long)q * l % MOD;

Wrong Way:

long ans = (long)(q * l % MOD);

Math

Greatest Common Divisor

private int gcd(int x, int y)
{
    if (x == 0) return y;
    return gcd(y % x, x);
}

Least Common Multiple

int l = a / gcd(a, b) * b;

Compare the square instead of the square root.

long distance2 = x * x + y * y;
if (distance2 <= bombI[2] * bombI[2])
{
    graph[i][j] = 1;
}

Beware of integer overflow, add i>0 in for loop

public class Solution
{
    public int RangeBitwiseAnd(int left, int right)
    {
        int result = left;
        for (int i = left + 1; i <= right && i > 0; i++)
        {
            result = result & i;
            if (result == 0)
            {
                return 0;
            }
        }

        return result;
    }
}

Without i > 0, if right is int.MaxValue, then the next value will be int.MinValue. Thus the result will be wrong.

Max/Min

private int Min(params int[] values)
{
    int result = values[0];
    for (int i = 1; i < values.Length; i++)
    {
        result = Math.Min(result, values[i]);
    }
    return result;
}

Strings

Using StringBuilder to concatenate strings.

Implements

228 Trie 137 Binary Search Tree Iterator 297 Serialize and Deserialize Binary Tree Better finish this first.