Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

type Position struct {
	X int
	Y int
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	n, err := nextInt(sc)
	if err != nil {
		panic(err)
	}
	for i := 0; i < n; i++ {
		strX := nextText(sc)
		strY := nextText(sc)
		fmt.Println(calcLcs(strX, strY))
	}
}

func calcLcs(strX, strY string) int {
	return lcs(strX, strY, Position{0, 0}, make(map[Position]int))
}

func lcs(strX string, strY string, position Position, memo map[Position]int) int {
	if position.X >= len(strX) || position.Y >= len(strY) {
		return 0
	}
	if v, ok := memo[position]; ok {
		return v
	}
	if strX[position.X] == strY[position.Y] {
		result := lcs(strX, strY, Position{position.X + 1, position.Y + 1}, memo)
		memo[position] = result + 1
		return memo[position]
	} else {
		result1 := lcs(strX, strY, Position{position.X + 1, position.Y}, memo)
		result2 := lcs(strX, strY, Position{position.X, position.Y + 1}, memo)
		var result int
		if result1 > result2 {
			result = result1
		} else {
			result = result2
		}
		memo[position] = result
		return result
	}
}

func nextInt(sc *bufio.Scanner) (int, error) {
	sc.Scan()
	return strconv.Atoi(sc.Text())
}

func nextText(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

C++: #include <bits/stdc++.h>
#define rep(i,j,k) for(int i=(int)j;i<(int)k;i++)
#define itrep(i,x) for(auto i=(x).begin(); i!=(x).end();i++)
#define Sort(x) sort((x).begin(),(x).end())
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define vi vector<int>
//#define INF 1<<31-1
#define INFL 1e18
#define MOD 1000000007
#define pb push_back
#define MP make_pair
#define PI 3.1415926535
typedef long long int ll;
//typedef std::pair<int,int> P;
int D=1;
int dx[4]={0,1,0,-1},dy[4]={-1,0,1,0};
int INF=INT_MAX;

using namespace std;

int main(){
    string s,t;
    int n;
    cin>>n;
    rep(i,0,n){
        cin>>s>>t;
        vector<vector<int>> v(s.size()+1,vector<int>(t.size()+1));
        int ans=0;
        
        rep(i,0,s.size())v[i][0]=0;
        rep(i,0,t.size())v[0][i]=0;
        
        rep(i,1,s.size()+1){
            rep(j,1,t.size()+1){
                if(s[i]==t[j]){
                    v[i][j]=v[i-1][j-1]+1;
                }else {
                    v[i][j]=max(v[i-1][j],v[i][j-1]);
                }
            ans=max(ans,v[i][j]);
            }
        }
        cout<<ans<<endl;
    }
    
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
using ll=long long;
using vb=vector<bool>;
using vvb=vector<vb>;
using vd=vector<double>;
using vvd=vector<vd>;
using vi=vector<int>;
using vvi=vector<vi>;
using vl=vector<ll>;
using vvl=vector<vl>;
using pll=pair<ll,ll>;
using tll=tuple<ll,ll>;
using vs=vector<string>;
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define rep(i,n) range(i,0,n)
#define range(i,a,n) for(ll i=(a);i<(n);i++)
#define LINF ((ll)1ll<<60)
#define INF ((int)1<<30)
#define EPS (1e-9)
#define MOD (1000000007ll)
#define fcout(a) cout<<setprecision(a)<<fixed
#define fs first
#define sc second
#define PI 3.1415926535897932384

int dx[]={1,0,-1,0,1,-1,-1,1},dy[]={0,1,0,-1,1,1,-1,-1};
template<class S,class T>ostream&operator<<(ostream&os,pair<S,T>p){os<<"["<<p.first<<", "<<p.second<<"]";return os;};
template<class S>auto&operator<<(ostream&os,vector<S>t){bool a=1; for(auto s:t){os<<(a?"":" ")<<s;a=0;} return os;}
void OUT(bool b){cout<<(b?"YES":"NO")<<endl;}
void Out(bool b){cout<<(b?"Yes":"No")<<endl;}
void out(bool b){cout<<(b?"yes":"no")<<endl;}
template<class T>
void puta(T&&t){cout<<t<<endl;}
template<class H,class...T>
void puta(H&&h,T&&...t){cout<<h<<' ';puta(t...);}

int popcnt(int x){return __builtin_popcount(x);}
int popcnt(ll x){return __builtin_popcountll(x);}
int bsr(int x){return 31 - __builtin_clz(x);}
int bsr(ll x){return 63 - __builtin_clzll(x);}
int bsf(int x){return __builtin_ctz(x);}
int bsf(ll x){return __builtin_ctzll(x);}
template<class T>T chmax(T&a,T b){return a=a>b?a:b;}
template<class T>T chmin(T&a,T b){return a=a<b?a:b;}
/*他のライブラリを入れる場所*/

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	int d;
	cin>>d;
	rep(_,d){
		string s,t;
		cin>>s>>t;
		int n=s.size(),m=t.size();
		vvi dp(n+1,vi(m+1,0));
		rep(i,n){
			dp[i+1]=dp[i];
			rep(j,m){
				if(s[i]==t[j]){
					chmax(dp[i+1][j+1],dp[i][j]+1);
				}else{
					chmax(dp[i+1][j+1],dp[i+1][j]);
				}
			}
	//		cout<<dp[i]<<endl;
		}
	//	cout<<dp[n]<<endl;
		cout<<dp[n][m]<<endl;
	}
	return 0;
}

C++: #include <iostream>
#include <stdio.h>
#include <string>
#include <cmath>

#define MAX_LENGTH 1000
#define NIL -1
using namespace std;
//think easy make easy

int q;//num of datasets
string X;
string Y;
char map[MAX_LENGTH+1][MAX_LENGTH+1];

int findMaxLength(int x,int y){//x:Xの終端.y:Yの終端(0オリジン)
	int val;

	if(x == 0 || y == 0) return 0;

	if(map[x][y] == NIL){
		if(X.at(x) == Y.at(y)){
			val = findMaxLength(x-1,y-1) +1;
		}else{
			val = max(findMaxLength(x-1,y),findMaxLength(x,y-1));
		}
		map[x][y] = val;//メモ
		return val;
	}else return map[x][y];
}

int main(){
	
	scanf("%d",&q);

	for(int i=0;i<q;i++){
		cin >>X; cin >> Y;
		for(int i=0;i<X.size();i++){
			for(int j=0;j<Y.size();j++){
				map[i][j] = NIL;
			}
		}
	
		cout <<findMaxLength(X.size()-1,Y.size()-1) <<endl;
	}

	return 0;
}

C++: #include<iostream>
#include<string>
#include<algorithm>
using namespace std;
static const int N =1000;

int lcs(string X,string Y){
  int c[N+1][N+1];
  int m=X.size();
  int n=Y.size();
  int maxl=0;
  X=' '+X;
  Y=' '+Y;
  for(int i=0;i<=m;i++)c[i][0]=0;
  for(int j=1;j<=n;j++)c[0][j]=0;

  for(int i=1;i<=m;i++){
    for(int j=1;j<=n;j++){
      if(X[i]==Y[j]){
        c[i][j]=c[i-1][j-1]+1;
      }else{
        c[i][j]=max(c[i-1][j],c[i][j-1]);
      }
maxl=max(maxl,c[i][j]);
    }
  }
return maxl;
}

int main(){
  string s1,s2;
  int n;cin>>n;
  for(int i=0;i<n;i++){
    cin>>s1>>s2;
    cout<<lcs(s1,s2)<<endl;
  }
return 0;
}

C++: #include<iostream>
#include<string>
#include<algorithm>
using namespace std;
static const int N = 1000;

int lcs(string X, string Y) {
  int c[N + 1][N + 1];
  int m = X.size();
  int n = Y.size();
  int maxl = 0;
  X = ' ' + X;
  Y = ' ' + Y;
  for ( int i = 0; i <= m; i++ ) c[i][0] = 0;
  for ( int j = 1; j <= n; j++ ) c[0][j] = 0;

  for ( int i = 1; i <= m; i++ )
    for ( int j = 1; j <= n; j++ ) {
      if ( X[i] == Y[j] )
        c[i][j] = c[i - 1][j - 1] + 1;
      else
        c[i][j] = max(c[i - 1][j], c[i][j - 1]);
      maxl = max(maxl, c[i][j]);
    }

  return maxl;
}

int main() {
  string s1, s2;
  int n; cin >> n;
  for ( int i = 0; i < n; i++ ) {
    cin >> s1 >> s2;
    cout << lcs(s1, s2) << endl;
  }
  return 0;
}

C++: #include <stdio.h>
#include <string.h>
#define N 1000

void Ics(char *X, char *Y)
{
   int c[N][N];
   int m, n, i, j;

   m = strlen(X);
   n = strlen(Y);

   for ( i = 1; i <= m; i++ ) c[i][0] = 0;
   for ( j = 0; j <= n; j++ ) c[0][j] =0;
   for ( i = 1; i <= m; i++ ) {
      for ( j = 1; j <=n; j++ ) {
         if ( X[ i - 1 ] == Y[ j - 1] ) c[ i ][ j ] = c[ i - 1 ][ j - 1 ] + 1;
         else if ( c[ i - 1 ][ j ] >= c[ i ][ j - 1 ] )c[ i ][ j ] = c[ i - 1 ][ j ];
         else c[ i ][ j ] = c[ i ][ j - 1 ];
      }
   }
   printf("%d\n", c[ m ][ n ]);
}
     
int main()
{
   int n, i;
   char X[N], Y[N];

   scanf("%d", &n);
   for ( i = 0; i < n; i++ ) {
      scanf("%s%s", X, Y);
      Ics(X, Y);
   }
   return 0;
}