HackerRank LCS Returns Problem Solution
In this post, we will solve HackerRank LCS Returns Problem Solution.
Given two strings, a and b, find and print the total number of ways to insert a character at any position in string a such that the length of the Longest Common Subsequence of characters in the two strings increases by one.
Input Format
The first line contains a single string denoting a.
The second line contains a single string denoting b.
Constraints
Scoring
1a,b 5000
- Strings a and b are alphanumeric (i.e., consisting of arabic digits and/or upper and lower case English letters).
- The new character being inserted must also be alphanumeric (i.e., a digit or upper/lower case English letter).
Output Format
Print a single integer denoting the total number of ways to insert a character into string a in such a way that the length of the longest common subsequence of a and b increases by
one.
Sample Input
aa
baaa
Sample Output
4
LCS Returns C Solution
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
int d1[5002][5002];
int d2[5002][5002];
char s1[6000],s2[6000];
int cc[256];
int main() {
int i,j,l1,l2,p,c,ret=0;
scanf("%s %s",s1,s2);
l1=strlen(s1),l2=strlen(s2);
for(i=1;i<=l1;i++) for(j=1;j<=l2;j++) {
d1[i][j]=d1[i-1][j];
if (d1[i][j-1]>d1[i][j]) d1[i][j]=d1[i][j-1];
if (s1[i-1]==s2[j-1]) d1[i][j]=d1[i-1][j-1]+1;
}
for(i=l1-1;i>=0;i--) for(j=l2-1;j>=0;j--) {
d2[i][j]=d2[i+1][j];
if (d2[i][j+1]>d2[i][j]) d2[i][j]=d2[i][j+1];
if (s1[i]==s2[j]) d2[i][j]=d2[i+1][j+1]+1;
}
for(i=0;i<=l1;i++) {
for(j=0;j<l2;j++) if (d1[i][j]+d2[i][j+1]==d1[l1][l2]) cc[s2[j]]=1;
for(j=0;j<128;j++) if (cc[j]) ret++,cc[j]=0;
}
printf("%d\n",ret);
return 0;
}
LCS Returns C++ Solution
#include <fstream>
#include <iostream>
#include <string>
#include <complex>
#include <math.h>
#include <set>
#include <vector>
#include <map>
#include <queue>
#include <stdio.h>
#include <stack>
#include <algorithm>
#include <list>
#include <sstream>
#include <ctime>
#include <memory.h>
#include <assert.h>
#include <unordered_map>
#include <limits.h>
#include <bitset>
#include <unordered_set>
using namespace std;
const long long bs = 1000000007;
static const int INF = 0x3f3f3f3f;
static const long long INFL = 0x3f3f3f3f3f3f3f3fLL;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vector<int> > vvi;
#define REP(i, n) for (int i=0; i < (int)(n); ++i)
#define pb push_back
#define mp make_pair
struct cmp {
bool operator()(int &a, int &b) { return a < b; }
};
template<typename T>
string sv(vector<T> &v) {
if (v.size() == 0) return "[]";
stringstream ss;
ss << "[";
for (std::size_t i = 0; i < v.size() - 1; ++i) ss << v[i] << ", ";
ss << v[v.size() - 1] << "]";
return ss.str();
}
template<typename T>
void sv2d(vector<vector<T>> &v) {
for (int i = 0; i < v.size(); i++) cout << sv(v[i]) << i+1 << " " << endl;
}
string a,b;
void dfs(vvi &dp, vvi &trace, int i, int j) {
if (i == 0 || j == 0) {
//trace[i][j]=0;
return;
}
if (a[i-1] == b[j-1] && trace[i-1][j-1] != 1 ) {
trace[i-1][j-1] = 1;
dfs(dp,trace,i-1,j-1);
}
if (dp[i-1][j] == dp[i][j] && trace[i-1][j] != 1) {
trace[i-1][j] = 1;
dfs(dp,trace,i-1,j);
}
if (dp[i][j-1] == dp[i][j] && trace[i][j-1] != 1) {
trace[i][j-1] = 1;
dfs(dp,trace,i,j-1);
}
}
int main() {
string tmp;
cin>>tmp>>b;
a.resize(tmp.size()*2);
for (int i = 0; i < tmp.size(); i++) {
a[i*2]= '_';
a[i*2+1] = tmp[i];
}
vvi dp(a.size()+1, vi(b.size()+1, 0));
vvi trace(a.size()+1, vi(b.size()+1, 0));
unordered_set<int> cs;
REP(i,b.size()) cs.insert(b[i]);
int lcs = 0;
for (int i = 0; i < a.size(); i++) {
for (int j = 0; j < b.size(); j++) {
if (a[i]==b[j]) {
dp[i+1][j+1] = dp[i][j]+1;
lcs = max(lcs, dp[i+1][j+1]);
//dp[i+1][j+1] = dp[i+1][j]+1;
} else {
dp[i+1][j+1] = max(dp[i+1][j],dp[i][j+1]);
//dp[i+1][j+1] = dp[i+1][j];
}
}
}
//sv2d(dp); cout << endl;
dfs(dp,trace,dp.size()-1,dp[0].size()-1);
//sv2d(trace);
//cout << endl;
int ans = 0;
for (auto &c : cs) {
vector<bool>memo(dp.size());
for (int j = 0; j < b.size(); j++) {
if (b[j] != c) continue;
for (int i = 0; i < a.size(); i++) {
if (i%2!=0) continue;
if (memo[i]) continue;
if (trace[i+1][j+1] == 1 && dp[i+1][j+1]==dp[i+1][j]) {
ans++;
memo[i] = true;
}
}
}
for (int j = 0; j < b.size(); j++) {
if (b[j] != c) continue;
if (trace[a.size()][j]==1) {
ans++;
break;
}
}
}
cout << ans << endl;
return 0;
}
LCS Returns C Sharp Solution
using System.CodeDom.Compiler;
using System.Collections.Generic;
using System.Collections;
using System.ComponentModel;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime.Serialization;
using System.Text.RegularExpressions;
using System.Text;
using System;
class Result
{
/*
* Complete the 'tutzkiAndLcs' function below.
*
* The function is expected to return an INTEGER.
* The function accepts following parameters:
* 1. STRING a
* 2. STRING b
*/
public static int tutzkiAndLcs(string a, string b)
{
int res = 0;
int n = a.Length, m = b.Length;
int[][] dpp = new int[n + 1][];
int[][] dps = new int[n + 1][];
for (int i = 0; i <= n; i++)
{
dpp[i] = new int[m + 1];
dps[i] = new int[m + 1];
}
for (int i = 0; i < n; i++)
{
for (int j = 0; j < m; j++)
{
if (a[i] == b[j]) dpp[i + 1][j + 1] = dpp[i][j] + 1;
else dpp[i + 1][j + 1] = Math.Max(dpp[i][j + 1], dpp[i + 1][j]);
}
}
for (int i = n - 1; i >= 0; i--)
{
for (int j = m - 1; j >= 0; j--)
{
if (a[i] == b[j]) dps[i][j] = dps[i + 1][j + 1] + 1;
else dps[i][j] = Math.Max(dps[i][j + 1], dps[i + 1][j]);
}
}
int r = dpp[n][m];
bool[] bl;
int cur;
for (int i = 0; i <= n; i++)
{
bl = new bool[256];
for (int j = 0; j < m; j++)
{
if (bl[b[j]]) continue;
cur = dpp[i][j] + dps[i][j + 1];
if (r == cur)
{
res++;
bl[b[j]] = true;
}
}
}
return res;
}
}
class Solution
{
public static void Main(string[] args)
{
TextWriter textWriter = new StreamWriter(@System.Environment.GetEnvironmentVariable("OUTPUT_PATH"), true);
string a = Console.ReadLine();
string b = Console.ReadLine();
int result = Result.tutzkiAndLcs(a, b);
textWriter.WriteLine(result);
textWriter.Flush();
textWriter.Close();
}
}
LCS Returns Java Solution
import java.io.*;
import java.util.*;
public class LCSReturns {
BufferedReader br;
PrintWriter out;
StringTokenizer st;
boolean eof;
void solve() throws IOException {
String a = nextToken();
String b = nextToken();
int n = a.length();
int m = b.length();
int[][] pref = new int[n + 1][m + 1];
int[][] suff = new int[n + 1][m + 1];
for (int i = 0; i < n; i++)
for (int j = 0; j < m; j++) {
if (a.charAt(i) == b.charAt(j)) {
pref[i + 1][j + 1] = pref[i][j] + 1;
} else {
pref[i + 1][j + 1] = Math.max(pref[i + 1][j],
pref[i][j + 1]);
}
}
for (int i = n - 1; i >= 0; i--)
for (int j = m - 1; j >= 0; j--) {
if (a.charAt(i) == b.charAt(j)) {
suff[i][j] = suff[i + 1][j + 1] + 1;
} else {
suff[i][j] = Math.max(suff[i][j + 1], suff[i + 1][j]);
}
}
int cur = pref[n][m];
int ret = 0;
for (int i = 0; i <= n; i++) {
boolean[] used = new boolean[256];
for (int j = 0; j < m; j++) {
if (used[b.charAt(j)]) {
continue;
}
int now = pref[i][j] + suff[i][j + 1] + 1;
if (now == cur + 1) {
used[b.charAt(j)] = true;
ret++;
}
}
}
out.println(ret);
}
LCSReturns() throws IOException {
br = new BufferedReader(new InputStreamReader(System.in));
out = new PrintWriter(System.out);
solve();
out.close();
}
public static void main(String[] args) throws IOException {
new LCSReturns();
}
String nextToken() {
while (st == null || !st.hasMoreTokens()) {
try {
st = new StringTokenizer(br.readLine());
} catch (Exception e) {
eof = true;
return null;
}
}
return st.nextToken();
}
String nextString() {
try {
return br.readLine();
} catch (IOException e) {
eof = true;
return null;
}
}
int nextInt() throws IOException {
return Integer.parseInt(nextToken());
}
long nextLong() throws IOException {
return Long.parseLong(nextToken());
}
double nextDouble() throws IOException {
return Double.parseDouble(nextToken());
}
}
LCS Returns JavaScript Solution
function processData(input) {
var inputStrings = input.split('\n');
var A = inputStrings[0];
var B = inputStrings[1];
var lcsPrefixes = lcs(A, B);
var lcsSuffixes = lcs(A.split('').reverse().join(''), B.split('').reverse().join(''));
var numberOfSolutions = insertionSolutionsIncreasingLcsLengthByOne(lcsPrefixes, lcsSuffixes, B);
console.log(numberOfSolutions);
function lcs(a, b) {
var A = a.split('');
var B = b.split('');
A.unshift(null);
B.unshift(null);
var rows = A.length;
var columns = B.length;
var lcsMatrix = matrix(rows, columns);
for (var i = 0; i < rows; ++i) {
for (var j = 0; j < columns; ++j) {
var value;
if (i == 0 || j == 0) {
value = 0;
} else if (A[i] == B[j]) {
value = lcsMatrix[i - 1][j - 1] + 1;
} else {
value = Math.max(lcsMatrix[i][j - 1], lcsMatrix[i - 1][j]);
}
lcsMatrix[i][j] = value;
}
}
return lcsMatrix;
function matrix(rows, columns) {
var matrix = [];
for (var i = 0; i < rows; ++i) {
var rowBuffer = new ArrayBuffer(columns * 2);
matrix[i] = new Int16Array(rowBuffer);
}
return matrix;
}
}
function insertionSolutionsIncreasingLcsLengthByOne(lcsPrefixes, lcsSuffixes, insertionSource) {
var numberOfRows = lcsPrefixes.length;
var numberOfColumns = lcsPrefixes[0].length;
var targetLength = lcsPrefixes[numberOfRows - 1][numberOfColumns - 1] + 1;
var B = insertionSource.split('');
B.unshift(null);
var numberOfSolutions = 0;
for (var i = 1; i <= numberOfRows; ++i) {
var solutions = [];
for (var j = 1; j < B.length; ++j) {
var lcsLengthOfPrefixes = lcsPrefixes[i - 1][j - 1];
var lcsLengthOfSuffixes = i < numberOfRows ?
lcsSuffixes[numberOfRows - i][numberOfColumns - (j + 1)] :
0;
var lcsLength = lcsLengthOfPrefixes + 1 + lcsLengthOfSuffixes;
if (lcsLength == targetLength) {
addSolutionToList(B[j], solutions);
} else if (lcsLength > targetLength) {
removeSolutionFromList(B[j], solutions);
}
}
numberOfSolutions += solutions.length;
}
return numberOfSolutions;
function addSolutionToList(solution, list) {
list.indexOf(solution) < 0 && list.push(solution);
}
function removeSolutionFromList(solution, list) {
var solutionIndex = list.indexOf(solution);
solutionIndex >= 0 && list.splice(solutionIndex, 1);
}
}
}
process.stdin.resume();
process.stdin.setEncoding("ascii");
_input = "";
process.stdin.on("data", function (input) {
_input += input;
});
process.stdin.on("end", function () {
processData(_input);
});