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LongestCommonSubsequence.java
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LongestCommonSubsequence.java
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/*
*HackerRank : A subsequence is a sequence that can be derived from another sequence by deleting some elements without
* changing the order of the remaining elements. Longest common subsequence
* (LCS) of 2 sequences is a subsequence, with maximal length, which is common to both the sequences.
*
* Sample Input
*
* 5 6 (number of items in each coming string or arrays)
* 1 2 3 4 1
* 3 4 1 2 1 3
* Sample Output (Sample output may have multiple ansers (1 2 3 , 3 4 1 , 1 2 1), show at least one)
* 1 2 3
*/
//longest common subsequence
//O(m*n)
public class LongestCommonSubsequence {
int array1[];
int array2[];
int table [][];
char symbolTable [][];
String result;
public static void main(String[] args) {
/* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
LongestCommonSubsequence lcs = new LongestCommonSubsequence();
Scanner scanner = new Scanner(System.in);
int length1 = scanner.nextInt();
int length2 = scanner.nextInt();
lcs.array1 = new int[length1];
lcs.array2 = new int[length2];
for(int i=0; i<length1; i++)
lcs.array1[i] = scanner.nextInt();
for(int i=0; i<length2; i++)
lcs.array2[i] = scanner.nextInt();
lcs.table = new int[lcs.array1.length+1][lcs.array2.length+1];
lcs.symbolTable = new char[lcs.array1.length+1][lcs.array2.length+1];
lcs.result = "";
lcs.findLongestSubsequence();
int m = lcs.array1.length;
int n = lcs.array2.length;
lcs.printLCS(m, n);
System.out.println(lcs.result);
}
public void findLongestSubsequence()
{
int i = 0, j=0;
for(i=0; i<= array1.length; i++)
table[i][0] = 0;
for(i=0; i<= array2.length; i++)
table[0][i] = 0;
for(i=1; i< table.length; i++)
{
for(j=1; j< table[0].length; j++)
{
if(array1[i-1] == array2[j-1])
{
table[i][j] = table[i-1][j-1]+1;
symbolTable[i][j] = '/';
}
else
{
if(table[i][j-1] > table [i-1][j])
{
table[i][j] = table[i][j-1];
symbolTable[i][j] = '-';
}
else
{
table[i][j] = table[i-1][j];
symbolTable[i][j] = '|';
}
}
}
}
}
public void printLCS(int m, int n)
{
if( m == 0 || n == 0)
return;
if(symbolTable[m][n] == '/')
{
printLCS(m-1, n-1);
result = result + array1[m-1]+" ";
}
else if(symbolTable[m][n] == '|')
printLCS(m-1, n);
else
printLCS(m, n-1);
}
}