这可以用动态规划在O(n²)中解决。同样的Python代码是这样的:-

def LIS(numlist):
    LS = [1]
    for i in range(1, len(numlist)):
        LS.append(1)
        for j in range(0, i):
            if numlist[i] > numlist[j] and LS[i]<=LS[j]:
                LS[i] = 1 + LS[j]
    print LS
    return max(LS)

numlist = map(int, raw_input().split(' '))
print LIS(numlist)

输入:5 19 5 81 50 28 29 1 83 23

输出将是:[1,2,1,3,3,3,4,1,5,3] 5

输出列表的list_index是输入列表的list_index。输出列表中给定list_index的值表示该list_index的最长递增子序列长度。

求最长递增子序列(LIS)的O(NLog(N))递归DP方法

解释

该算法涉及创建节点格式为(a,b)的树。

A表示到目前为止我们考虑添加到有效子序列的下一个元素。

B表示剩余子数组的起始索引，如果a被添加到目前为止我们所拥有的子数组的末尾，则下一个决策将从该子数组开始。

算法

We start with an invalid root (INT_MIN,0), pointing at index zero of the array since subsequence is empty at this point, i.e. b = 0. Base Case: return 1 if b >= array.length. Loop through all the elements in the array from the b index to the end of the array, i.e i = b ... array.length-1. i) If an element, array[i] is greater than the current a, it is qualified to be considered as one of the elements to be appended to the subsequence we have so far. ii) Recurse into the node (array[i],b+1), where a is the element we encountered in 2(i) which is qualified to be appended to the subsequence we have so far. And b+1 is the next index of the array to be considered. iii) Return the max length obtained by looping through i = b ... array.length. In a case where a is bigger than any other element from i = b to array.length, return 1. Compute the level of the tree built as level. Finally, level - 1 is the desired LIS. That is the number of edges in the longest path of the tree.

注意:算法的记忆部分被省略了，因为它是从树中清除的。

随便举个例子 标记为x的节点从DB内存值中获取。

Java实现

public int lengthOfLIS(int[] nums) {
            return LIS(nums,Integer.MIN_VALUE, 0,new HashMap<>()) -1;
    }
    public int LIS(int[] arr, int value, int nextIndex, Map<String,Integer> memo){
        if(memo.containsKey(value+","+nextIndex))return memo.get(value+","+nextIndex);
        if(nextIndex >= arr.length)return 1;

        int max = Integer.MIN_VALUE;
        for(int i=nextIndex; i<arr.length; i++){
            if(arr[i] > value){
                max = Math.max(max,LIS(arr,arr[i],i+1,memo));
            }
        }
        if(max == Integer.MIN_VALUE)return 1;
        max++;
        memo.put(value+","+nextIndex,max);
        return max;
    }

O(n²)java实现:

void LIS(int arr[]){
        int maxCount[]=new int[arr.length];
        int link[]=new int[arr.length];
        int maxI=0;
        link[0]=0;
        maxCount[0]=0;

        for (int i = 1; i < arr.length; i++) {
            for (int j = 0; j < i; j++) {
                if(arr[j]<arr[i] && ((maxCount[j]+1)>maxCount[i])){
                    maxCount[i]=maxCount[j]+1;
                    link[i]=j;
                    if(maxCount[i]>maxCount[maxI]){
                        maxI=i;
                    }
                }
            }
        }


        for (int i = 0; i < link.length; i++) {
            System.out.println(arr[i]+"   "+link[i]);
        }
        print(arr,maxI,link);

    }

    void print(int arr[],int index,int link[]){
        if(link[index]==index){
            System.out.println(arr[index]+" ");
            return;
        }else{
            print(arr, link[index], link);
            System.out.println(arr[index]+" ");
        }
    }

这可以用动态规划在O(n²)中解决。同样的Python代码是这样的:-

def LIS(numlist):
    LS = [1]
    for i in range(1, len(numlist)):
        LS.append(1)
        for j in range(0, i):
            if numlist[i] > numlist[j] and LS[i]<=LS[j]:
                LS[i] = 1 + LS[j]
    print LS
    return max(LS)

numlist = map(int, raw_input().split(' '))
print LIS(numlist)

输入:5 19 5 81 50 28 29 1 83 23

输出将是:[1,2,1,3,3,3,4,1,5,3] 5

输出列表的list_index是输入列表的list_index。输出列表中给定list_index的值表示该list_index的最长递增子序列长度。

下面是O(n^2)算法的Scala实现:

object Solve {
  def longestIncrSubseq[T](xs: List[T])(implicit ord: Ordering[T]) = {
    xs.foldLeft(List[(Int, List[T])]()) {
      (sofar, x) =>
        if (sofar.isEmpty) List((1, List(x)))
        else {
          val resIfEndsAtCurr = (sofar, xs).zipped map {
            (tp, y) =>
              val len = tp._1
              val seq = tp._2
              if (ord.lteq(y, x)) {
                (len + 1, x :: seq) // reversely recorded to avoid O(n)
              } else {
                (1, List(x))
              }
          }
          sofar :+ resIfEndsAtCurr.maxBy(_._1)
        }
    }.maxBy(_._1)._2.reverse
  }

  def main(args: Array[String]) = {
    println(longestIncrSubseq(List(
      0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15)))
  }
}

c++中最简单的LIS解决方案，具有O(nlog(n))时间复杂度

#include <iostream>
#include "vector"
using namespace std;

// binary search (If value not found then it will return the index where the value should be inserted)
int ceilBinarySearch(vector<int> &a,int beg,int end,int value)
{
    if(beg<=end)
    {
        int mid = (beg+end)/2;
        if(a[mid] == value)
            return mid;
        else if(value < a[mid])
            return ceilBinarySearch(a,beg,mid-1,value);
        else
            return ceilBinarySearch(a,mid+1,end,value);

    return 0;
    }

    return beg;

}
int lis(vector<int> arr)
{
    vector<int> dp(arr.size(),0);
    int len = 0;
    for(int i = 0;i<arr.size();i++)
    {
        int j = ceilBinarySearch(dp,0,len-1,arr[i]);
        dp[j] = arr[i];
        if(j == len)
            len++;

    }
    return len;
}

int main()
{
    vector<int> arr  {2, 5,-1,0,6,1,2};
    cout<<lis(arr);
    return 0;
}

输出: 4