Implement LIS using recursion and top down dp efficiently.

How to implement LIS(Longest Increasing Subsequence) using recursion and top down dp efficiently?

There you go :

Dear @rashedcs

please follow the link (courtesy :- MIT OCW)

And here’s a problem and it’s successful submition

Problem link:-

#include <iostream>
#include <string.h>
#include <stdio.h>

using namespace std;

#define ARRAY_SIZE(A) sizeof(A)/sizeof(A[0])
// Binary search (note boundaries in the caller)
// A[] is ceilIndex in the caller
int CeilIndex(int A[], int l, int r, int key) {
int m;

while( r - l > 1 ) {
    m = l + (r - l)/2;
    (A[m] >= key ? r : l) = m; // ternary expression returns an l-value

return r;

 int LongestIncreasingSubsequenceLength(int A[], int size) {
 // Add boundary case, when array size is one

int *tailTable   = new int[size];
int len; // always points empty slot

memset(tailTable, 0, sizeof(tailTable[0])*size);

tailTable[0] = A[0];
len = 1;
for( int i = 1; i < size; i++ ) {
    if( A[i] < tailTable[0] )
        // new smallest value
        tailTable[0] = A[i];
    else if( A[i] > tailTable[len-1] )
        // A[i] wants to extend largest subsequence
        tailTable[len++] = A[i];
        // A[i] wants to be current end candidate of an existing subsequence
        // It will replace ceil value in tailTable
        tailTable[CeilIndex(tailTable, -1, len-1, A[i])] = A[i];

delete[] tailTable;

return len;
int A[1000009]={0}; 
int main() {
int n,i;

printf("%d\n",LongestIncreasingSubsequenceLength(A, n));

return 0;

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