Go: package main

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

// define
var (
	sc = bufio.NewScanner(os.Stdin)
)

func bordersInt(in_map [][]int, invalid int) [][]int{
	H, W := len(in_map), len(in_map[0])
	out_map := make([][]int, H+2)
	for h:=0; h<H+2; h++ {
		out_map[h] = make([]int, W+2)
		for w:=0; w<W+2; w++ {
			out_map[h][w] = invalid
		}
	}
	for h:=0; h<H; h++{
		for w:=0; w<W; w++{
			out_map[h+1][w+1] = in_map[h][w] 
		}
	}
	return out_map
}

func bordersString(in_map [][]string, invalid string) [][]string{
	H, W := len(in_map), len(in_map[0])
	out_map := make([][]string, H+2)
	for h:=0; h<H+2; h++ {
		out_map[h] = make([]string, W+2)
		for w:=0; w<W+2; w++ {
			out_map[h][w] = invalid
		}
	}
	for h:=0; h<H; h++{
		for w:=0; w<W; w++{
			out_map[h+1][w+1] = in_map[h][w] 
		}
	}
	return out_map
}

func scanIntLine(len int) []int{
	arr := make([]int, len)
	for i:=0; i<len; i++{
		sc.Scan()
		tmp, err := strconv.Atoi(sc.Text())
		if err == nil{
			arr[i] = tmp
		}
	}
	return arr
}

func scanStringLine(len int) []string{
	arr := make([]string, len)
	for i:=0; i<len; i++{
		sc.Scan()
		arr[i] = sc.Text()
	}
	return arr
}

func scanIntSplit(len int) []int{
	arr := make([]int, len)
	sc.Scan()
	for i, v := range strings.Split(sc.Text(), " "){
		tmp, err := strconv.Atoi(v)
		if err == nil{
			arr[i] = tmp
		}
	}
	return arr
}

func maxInt(args... int) int{
	sort.Ints(args)
	return args[len(args)-1]
}

func main(){
	buf := make([]byte, 0)
    sc.Buffer(buf, 1000000009)
	var n int 
	fmt.Scan(&n)
	dp := make([][]int, 1003)
	for i:=0; i<1003; i++ {
		dp[i] = make([]int, 1003)
	}
	input_lines := scanStringLine(2*n)
	for i:=0; i<n; i++ {
		S, T := input_lines[2*i], input_lines[2*i+1]
		lenS, lenT := len(S), len(T)
		for i:=1; i<lenS+1; i++ {
			for j:=1; j<lenT+1; j++ {
				if S[i-1] == T[j-1] {
					dp[i][j] = maxInt(dp[i-1][j-1]+1, dp[i-1][j], dp[i][j-1])
				} else {
					dp[i][j] = maxInt(dp[i-1][j], dp[i][j-1])
				}
			}
		}
		fmt.Println(dp[lenS][lenT])
	}
}

C++: #include <iostream>
#include <string>

using namespace std;
 
 
int main(){
 
  string str1;
  string str2;
  int n,s1,s2;
  int c[1001][1001] = {{}};
  int max = 0;
 
  cin >> n;
 
  for(int i = 0;i < n;i++){
 
    cin >> str1 >> str2;
 
    str1 = ' ' + str1;
    str2 = ' ' + str2;
 
 
    s1 = str1.size();
    s2 = str2.size();
 
    for(int j = 1;j < s1;j++){
      for(int k = 1;k < s2;k++){
    if(str1[j] == str2[k]){
      c[j][k] = c[j - 1][k - 1] + 1;
      if(c[j][k] > max) max = c[j][k];
    }
    else if(c[j - 1][k] > c[j][k - 1]){
      c[j][k] =  c[j - 1][k];
    }
    else {
      c[j][k] = c[j][k - 1];
    }
      }
    }
 
 
    cout << max << endl;
       
    max = 0;
 
    for(int j = 0;j <= s1;j++){
      for(int k = 0;k <= s2;k++){
        c[j][k] = 0;
      }
    }
  }
}

C++: #include <string>
#include <iostream>
#include <algorithm>

#define MAX_X 1000
#define MAX_Y 1000
using namespace std;

string X, Y;
int dp[MAX_X + 1][MAX_Y + 1] = {0};

void solve() {
    for (int i = 0; i <= X.size(); ++i) {
        for (int j = 0; j <= Y.size(); ++j) {
            if (i == 0 || j == 0)
                dp[i][j] = 0;
            else if (X[i] == Y[j])
                dp[i][j] = max(dp[i - 1][j - 1] + 1, max(dp[i][j - 1], dp[i - 1][j]));
            else
                dp[i][j] = max(dp[i][j - 1], dp[i - 1][j]);
        }
    }

    return;
}

int main() {
    int q;
    cin >> q;
    for (int i = 0; i < q; ++i) {
        cin >> X >> Y;
        solve();
        printf("%d\n", dp[X.size()][Y.size()]);
    }
}

C++: #include <iostream>
#include <string>
using namespace std;

int lcs(string X, string Y) {
  int cs[1001][1001];
  int m = X.size();
  int n = Y.size();
  int answer = 0;
  for (int i = 1; i <= m; i++) cs[i][0] = 0;
  for (int j = 1; j <= n; j++) cs[0][j] = 0;

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

  return answer;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  int n;
  cin >> n;

  string X, Y;

  for (int i = 0; i < n; i++) {
    cin >> X >> Y;
    cout << lcs(X, Y) << endl;
  }

  return 0;
}

C++: #include <string>
#include <iostream>
using namespace std;

int n;
string x, y;
bool mat[1000][1000];
int a[1000][1000];

int max(int i, int j) {
	int r = (!mat[i - 1][j] ? a[i - 1][j] : 0);
	r = ((!mat[i][j - 1] && a[i][j - 1] > r) ? a[i][j - 1] : r);
	return r > a[i - 1][j - 1] ? r : a[i - 1][j - 1];
}

int main(){
	cin >> n;
	for (int ia = 0; ia < n; ia++) {
		int ans = 0, p = 0;
		cin >> x >> y;
		for (int i = 0; i < x.length(); i++) {
			mat[i][0] = x[i] == y[0] ? true : false;
			a[i][0] = mat[i][0] ? 1 : 0;
		}
		for (int i = 1; i < y.length(); i++) {
			mat[0][i] = x[0] == y[i] ? true : false;
			a[0][i] = mat[0][i] ? 1 : 0;
		}
		for (int i = 1; i < x.length(); i++) {
			for (int j = 1; j < y.length(); j++) {
				mat[i][j] = x[i] == y[j] ? true : false;
				a[i][j] = max(i, j) + (mat[i][j] ? 1 : 0);
				if (a[i][j] > p) p = a[i][j];
			}
		}
		if (a[x.length() - 1][0] > p) p = a[x.length() - 1][0];
		if (a[0][y.length() - 1] > p) p = a[0][y.length() - 1];
		cout << p << endl;
	}


	return 0;
}

C++: #include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 1000000007
#define EPS 1e-10
#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;--i)
#define srep(i,s,t) for(int i=(int)(s);i<(int)(t);++i)
#define each(a,b) for(auto& (a): (b))
#define all(v) (v).begin(),(v).end()
#define len(v) (int)(v).size()
#define zip(v) sort(all(v)),v.erase(unique(all(v)),v.end())
#define cmx(x,y) x=max(x,y)
#define cmn(x,y) x=min(x,y)
#define fi first
#define se second
#define pb push_back
#define show(x) cout<<#x<<" = "<<(x)<<endl
#define spair(p) cout<<#p<<": "<<p.fi<<" "<<p.se<<endl
#define sar(a,n) cout<<#a<<":";rep(pachico,n)cout<<" "<<a[pachico];cout<<endl
#define svec(v) cout<<#v<<":";rep(pachico,v.size())cout<<" "<<v[pachico];cout<<endl
#define svecp(v) cout<<#v<<":";each(pachico,v)cout<<" {"<<pachico.first<<":"<<pachico.second<<"}";cout<<endl
#define sset(s) cout<<#s<<":";each(pachico,s)cout<<" "<<pachico;cout<<endl
#define smap(m) cout<<#m<<":";each(pachico,m)cout<<" {"<<pachico.first<<":"<<pachico.second<<"}";cout<<endl

using namespace std;

typedef pair<int,int> P;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<double> vd;
typedef vector<P> vp;
typedef vector<string> vs;

const int MAX_N = 100005;

const int MAX_SIZE = 52;

int LCS(const string& a, const string& b){
    int n = (int)a.size(), m = (int)b.size();
    vector<int> x(n), y(m);
    rep(i,n){
        x[i] = a[i]-'a';
        if(x[i] < 0){
            x[i] = a[i]-'A'+26;
        }
    }
    rep(i,m){
        y[i] = b[i]-'a';
        if(y[i] < 0){
            y[i] = b[i]-'A'+26;
        }
    }
    vector<vector<int> > vec(MAX_SIZE);
    for(int j = m-1; j >= 0; --j){
        vec[y[j]].push_back(j);
    }
    vector<int> xs(n+1, INF);
    xs[0] = -1;
    vector<P> nx(n+1,P(-INF,-INF));
    rep(i,n){
        vector<int>& ys = vec[x[i]];
        rep(j,(int)ys.size()){
            int k = lower_bound(xs.begin(),xs.end(),ys[j]) - xs.begin();
            xs[k] = ys[j];
            nx[k] = P(y[ys[j]], k-1);
        }
    }
    int l = lower_bound(xs.begin(),xs.end(),INF-1) - xs.begin();
    int id = l-1;
    int ans = 0;
    while(true){
        id = nx[id].second;
        if(id == -INF) break;
        ans++;
    }
    return ans;
}


int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int q;
    cin >> q;
    rep(i,q){
        string a,b;
        cin >> a >> b;
        cout << LCS(a,b) << "\n";
    }
    return 0;
}