Go: package main

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

var (
	nstr   func() string
	stdout *bufio.Writer
)

func init() {
	nstr = newReadString(os.Stdin)
	stdout = bufio.NewWriter(os.Stdout)
}

func main() {
	defer stdout.Flush()

	n := nint()
	xList := make([]string, n)
	yList := make([]string, n)

	for i:=0;i<n ;i++  {
		xList[i] = nstr()
		yList[i] = nstr()
	}

	for i := 0; i<n	; i++  {
		fmt.Println(lcs(xList[i], yList[i]))
	}

}

func lcs(x string, y string) int{
	var m = len(x)
	var n = len(y)

	c := make([][]int, m+1)
	for i:= range c{
		c[i] = make([]int, n+1)
	}
	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{
				c[i][j] = int(math.Max(float64(c[i-1][j]), float64(c[i][j-1])))
			}


		}
	}
	return c[m][n]

}


func newReadString(ior io.Reader) func() string {
	r := bufio.NewScanner(ior)
	r.Buffer(make([]byte, 1024), int(1e+11))
	r.Split(bufio.ScanWords)

	return func() string {
		if !r.Scan() {
			panic("Scan failed")
		}
		return r.Text()
	}
}

func nint64() int64 {
	i, err := strconv.ParseInt(nstr(), 0, 64)
	if err != nil {
		panic(err.Error())
	}
	return i
}

func nint() int {
	return int(nint64())
}

func getIntSlice(n int) []int {
	b := make([]int, n)
	for i := 0; i < n; i++ {
		b[i] = nint()
	}
	return b
}

func getStringSlice(n int) []string {
	b := make([]string, n)
	for i := 0; i < n; i++ {
		b[i] = nstr()
	}
	return b
}

func gcd(x, y int) int {
	if y == 0 {
		return x
	}
	return gcd(y, x%y)
}

func lcm(x, y int) int {
	return x * y / gcd(x, y)
}

func contains(s []int, e int) bool {
	for _, a := range s {
		if a == e {
			return true
		}
	}
	return false
}

func bin(i int, prefix bool) string {
	i64 := int64(i)

	if prefix {
		return "0b" + strconv.FormatInt(i64, 2)
	} else {
		return strconv.FormatInt(i64, 2)
	}
}

func strReverse(s string) string {
	runes := []rune(s)
	for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
		runes[i], runes[j] = runes[j], runes[i]
	}

	return string(runes)
}

C++: // Longest Common Subsequence
// 最長共通部分列
// 
#include <bits/stdc++.h>
using namespace std;
#define int long long
using P = pair<int, int>;
using V = vector<int>;
constexpr array<int, 4> dx = {1, 0, -1, 0}, dy = {0, 1, 0, -1};
constexpr int INF = 1234567890, MOD = 1000000000 + 7;
// constexpr int MOD = 998244353;
// constexpr int INF2 = 1000000000000000000LL+7;
template <class T>
bool chmax(T &a, const T &b)
{
    if (a < b)
    {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T &a, const T &b)
{
    if (b < a)
    {
        a = b;
        return 1;
    }
    return 0;
}
constexpr int ceil(int a, int b) { return (a + b - 1) / b; }
constexpr int gcd(int a, int b) { return b ? gcd(b, a % b) : a; }
constexpr int fact(int n) { return n > 1 ? n * fact(n - 1) % MOD : 1; }
constexpr int modpow(int a, int n)
{
    int rtn = 1;
    while (n > 0)
    {
        if (n & 1)
            rtn = rtn * a % MOD;
        a = a * a % MOD;
        n >>= 1;
    }
    return rtn;
}
int modinv(int a)
{
    int b = MOD, u = 1, v = 0;
    while (b)
    {
        int t = a / b;
        a -= t * b;
        swap(a, b);
        u -= t * v;
        swap(u, v);
    }
    u %= MOD;
    if (u < 0)
        u += MOD;
    return u;
}

signed main()
{
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout << setprecision(10);

    int n;
    cin >> n;
    for (int h = 0; h < n; h++)
    {
        string s, t;
        cin >> s >> t;

        vector<vector<int>> dp(s.size() + 1, vector<int>(t.size() + 1, 0));
        for (int i = 0; i < s.size(); i++)
        {
            for (int j = 0; j < t.size(); j++)
            {
                if (s[i] == t[j])
                {
                    dp[i + 1][j + 1] = dp[i][j] + 1;
                }
                else
                {
                    dp[i + 1][j + 1] = max(dp[i][j + 1], dp[i + 1][j]);
                }
            }
        }

        cout << dp[s.size()][t.size()] << endl;
    }
}

C++: #include <bits/stdc++.h>
using namespace std;

int lcs(string x, string y) {
  int m = x.size();
  int n = y.size();
  int maxl = 0;
  x = ' ' + x;
  y = ' ' + y;
  vector<vector<int>> c(m+1, vector<int> (n+1));

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

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;//??¨X[0]????????\?????????
	Y=' '+Y;//??¨Y[0]????????\?????????
	for(int i=1;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;
		int ans=lcs(s1,s2);
		if(ans<=20)cout<<ans<<endl;
		else cout<<"20"<<endl;
	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
int longest_common_subsequence_length(vector<int> &A, vector<int> &B){
	vector<vector<int>> dp(A.size() + 1, vector<int>(B.size() + 1, 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;
			} else {
				dp[i + 1][j + 1] = max(dp[i + 1][j], dp[i][j + 1]);
			}
		}
	}
	return dp[A.size()][B.size()];
}
int main(){
  int q;
  cin >> q;
  for (int i = 0; i < q; i++){
      string X, Y;
      cin >> X >> Y;
      vector<int> A(X.begin(), X.end());
      vector<int> B(Y.begin(), Y.end());
      cout << longest_common_subsequence_length(A, B) << endl;
  }
}

C++: #include <iostream>
#include <string>
#include <algorithm>
    using namespace std;
int lcs(string x,string y){
    int c[1010][1010];
    int m = x.size();
    int n = y.size();
    int maxl=0;
    x = ' '+x;
    y = ' '+y;
    for (int i=1; 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(){
    int q;
    string x;
    string y;
    scanf("%d",&q);
    for (int i=0; i<q; i++) {
        cin>>x>>y;
        cout<<lcs(x, y)<<endl;
    }
    return 0;
}

C++: #include "bits/stdc++.h"
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 = 1; 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;
}