DivideAndConquer-最大子数组问题

串行策略

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

namespace Maximum_subarray
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] originArray = { 13,-3,-25,20,-3,-16,-23,18,20,-7,12,-5,-22,15,-4,7};
            MaxSub maxsub = new MaxSub(originArray);
            var res = maxsub.Result;
            Console.Write("The Maximum subarray is : ");
            for (int i = res.Item1; i <= res.Item2; i++)
            {
                Console.Write("{0} ",originArray[i]);
            }
            Console.Write("\nAnd the sum is : {0}",res.Item3);
            Console.Write("\n");
            Console.Read();         
        }
    }
    class MaxSub
    {
        public MaxSub(int [] originarray)
        {
            OringinArray = originarray;
        }
        public int [] OringinArray
        {
            get;
            private set;
        }
        public Tuple<int,int,int> Result
        {
            get
            { return Generate(); }
            private set{}
        }
        private Tuple<int,int,int> Generate()
        {
            int firstIdx, lastIdx, sum;
            firstIdx = lastIdx = sum = 0;
            var turple = Tuple.Create(firstIdx, lastIdx, sum);
            for (int i = 0; i < OringinArray.Length;i++ )
            {
                sum += OringinArray[i];
                lastIdx = i;
                if (sum < OringinArray[i])
                {
                    firstIdx = i;
                    sum = OringinArray[i];
                }
                if (sum > turple.Item3)
                {
                    turple = Tuple.Create(firstIdx,lastIdx,sum);
                }
                //Console.Write("{0} {1} {2}\n", firstIdx, lastIdx, sum);
            }
            return turple;
        }

    }
}

分治策略

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

namespace MaxSubArray_DivAndCon
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] originArray = { 13, -3, -25, 20, -3, -16, -23, 18, 20, -7, 12, -5, -22, 15, -4, 7 };
            MaxSubArrayDAC maxSub = new MaxSubArrayDAC(originArray);
            var res = maxSub.Result;
            Console.Write("The Maximum subarray is : ");
            for (int i = res.Item1; i <= res.Item2; i++)
            {
                Console.Write("{0} ", originArray[i]);
            }
            Console.Write("\nAnd the sum is : {0}", res.Item3);
            Console.Write("\n");
            Console.Read();
        }
    }
    class MaxSubArrayDAC
    {
        public MaxSubArrayDAC(int [] originArray)
        {
            OriginArray = originArray;
        }
        public int[] OriginArray
        {
            get;
            private set;
        }
        public Tuple<int, int, int> Result
        {
            get{return Generate(0,OriginArray.Length-1);}
            private set { }
        }
        private Tuple<int,int,int> Generate(int leftIdx,int rightIdx)
        {
            if (leftIdx == rightIdx)
                return Tuple.Create(leftIdx, rightIdx, OriginArray[leftIdx]);
            else
            {
                int midIdx = (leftIdx + rightIdx) / 2;
                var leftTurple = Generate(leftIdx,midIdx);
                var rightTurple = Generate(midIdx+1,rightIdx);
                var midTurple = MaxCrossingSubArray(leftIdx, midIdx, rightIdx);
                if (leftTurple.Item3 > midTurple.Item3 && leftTurple.Item3 > rightTurple.Item3)
                    return leftTurple;
                else if (midTurple.Item3 > leftTurple.Item3 && midTurple.Item3 > rightTurple.Item3)
                    return midTurple;
                else
                    return rightTurple;
            }

        }
        private Tuple<int,int,int> MaxCrossingSubArray(int firIdx, int midIdx, int lastIdx)
        {
            int leftSum, rightSum,temp;
            leftSum = rightSum = temp = 0;
            int leftIdx, rightIdx;
            leftIdx = rightIdx = midIdx;
            for (int i = midIdx; i >= firIdx; i--)
            {
                temp += OriginArray[i];
                if (temp > leftSum)
                {
                    leftSum = temp;
                    leftIdx = i;
                }
            }
            temp = 0;
            for (int i = midIdx+1; i <= lastIdx; i++)
            {
                temp += OriginArray[i];
                if (temp > rightSum)
                {
                    rightSum = temp;
                    rightIdx = i;
                }
            }
            return Tuple.Create(leftIdx, rightIdx, leftSum + rightSum);
        }
    }
}