using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Algorithms.LinearAlgebra.Distances
{
    /// <summary>
    /// Implementation fo Manhattan distance.
    /// It is the sum of the lengths of the projections of the line segment between the points onto the coordinate axes.
    /// In other words, it is the sum of absolute difference between the measures in all dimensions of two points.
    ///
    /// Its commonly used in regression analysis.
    /// </summary>
    public static class Manhattan
    {
        /// <summary>
        /// Calculate Manhattan distance for two N-Dimensional points.
        /// </summary>
        /// <param name="point1">First N-Dimensional point.</param>
        /// <param name="point2">Second N-Dimensional point.</param>
        /// <returns>Calculated Manhattan distance.</returns>
        public static double Distance(double[] point1, double[] point2)
        {
            if (point1.Length != point2.Length)
            {
                throw new ArgumentException("Both points should have the same dimensionality");
            }

            // distance = |x1-y1| + |x2-y2| + ... + |xn-yn|
            return point1.Zip(point2, (x1, x2) => Math.Abs(x1 - x2)).Sum();
        }
    }
}
