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

constexpr int nil = -1;

class ILcs
{
public:
    using vvi = std::vector<std::vector<int>>;
    virtual int lcs() = 0;
    virtual int lcs(int i1, int i2) = 0;
};

class LcsLoop : public ILcs
{
public:

    LcsLoop(std::string str1, std::string str2)
        : str1 {" " + str1}
        , str2 {" " + str2}
        , dp {vvi(str1.size() + 1, std::vector<int>(str2.size() + 1))}
    {
        CalcLcs();
    }

    int lcs() override
    {
        return lcs(str1.size() - 1, str2.size() - 1);
    }

    int lcs(int i1, int i2) override
    {
        return dp[i1][i2];
    }

private:

    std::string str1;
    std::string str2;
    vvi         dp;
    
    void CalcLcs()
    {
        for (int i = 0; i < str1.size(); ++i)
            dp[i][0] = 0;
        for (int i = 0; i < str2.size(); ++i)
            dp[0][i] = 0;

        for (int i = 1; i < str1.size(); ++i)
        {
            for (int j = 1; j < str2.size(); ++j)
            {
                if (str1[i] == str2[j])
                    dp[i][j] = dp[i - 1][j - 1] + 1;
                else
                    dp[i][j] = std::max(dp[i][j - 1], dp[i - 1][j]);
            }
        }
    }
};

//class LcsReccursion : public ILcs
//{
//public:
//    LcsReccursion(const std::string& str1, const std::string& str2)
//        : str1 {str1}
//        , str2 {str2}
//        , dp {vvi(str1.size(), std::vector<int>(str2.size(), nil))}
//    {}
//
//    int lcs() override
//    {
//        return lcs(str1.size() - 1, str2.size() - 1);
//    }
//
//    int lcs(int i1, int i2) override
//    {
//        if (dp[i1][i2] != nil)
//            return dp[i1][i2];
//
//        if (i1 == 0 || i2 == 0)
//        {
//            if (i1 == 0 && i2 == 0) return dp[i1][i2] = (str1[i1] == str2[i2]);
//            else if (i1 == 0)       return dp[i1][i2] = std::max(lcs(i1, i2 - 1), (str1[i1] == str2[i2] ? 1 : 0));
//            else                    return dp[i1][i2] = std::max(lcs(i1 - 1, i2), (str1[i1] == str2[i2] ? 1 : 0));
//        }
//
//        dp[i1][i2] = std::max(lcs(i1 - 1, i2), lcs(i1, i2 - 1))
//            + (str1[i1] == str2[i2]);
//        return dp[i1][i2];
//    }
//
//private:
//
//    std::string str1;
//    std::string str2;
//    vvi         dp;
//};

void solve()
{
    using namespace std;

    int n;
    cin >> n;

    string s1, s2;

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

int main()
{
    solve();
    return 0;
}

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

int main(){
    int N;
    cin>>N;
    if(N>20){
        for(int i=0;i<N;i++){
            string inp1,inp2;
            cin>>inp1;
            cin>>inp2;
            int dp[101][101]={};
            for(int j=1;j<=inp1.size();j++){
                for(int k=1;k<=inp2.size();k++){
                    if(inp1[j]==inp2[k]){
                        dp[j][k]=dp[j-1][k-1]+1;
                    }else{
                        dp[j][k]=max(dp[j-1][k],dp[j][k-1]);
                    }
                }
            }
            cout<<dp[inp1.size()][inp2.size()]<<endl;
        }
    }else{
        for(int i=0;i<N;i++){
            string inp1,inp2;
            cin>>inp1;
            cin>>inp2;
            int dp[1001][1001]={};
            for(int j=1;j<=inp1.size();j++){
                for(int k=1;k<=inp2.size();k++){
                    if(inp1[j]==inp2[k]){
                        dp[j][k]=dp[j-1][k-1]+1;
                    }else{
                        dp[j][k]=max(dp[j-1][k],dp[j][k-1]);
                    }
                }
            }
            cout<<dp[inp1.size()][inp2.size()]<<endl;
        }
    }
    
    return 0;
}

C++: #include<cstdio>
#include<iostream>
#include<string>
#include<algorithm>
using namespace std;
#define N 1000

int lcs(string X,string Y){
  int c[N+1][N+1];
  int m=X.size();
  int n=Y.size();
  int maxcost=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]);
      }
      maxcost=max(maxcost,c[i][j]);
    }
  }
  return maxcost;
}

int main(){
  string s1,s2;
  int n;
  scanf("%d",&n);
  for(int i=0;i<n;i++){
    cin >> s1 >> s2;
    printf("%d\n",lcs(s1,s2));
  }
  return 0;
}

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

constexpr int MAX_XY = 1000;

int lx, ly, q, dp[MAX_XY][MAX_XY];
std::string sx, sy;

void fill_dp(){
    for(int i = 1; i <= lx; ++i){
        for(int j = 1; j <= ly; ++j){
            if(sx[i - 1] == sy[j - 1]) dp[i][j] = dp[i - 1][j - 1] + 1;
            else dp[i][j] = std::max(dp[i - 1][j], dp[i][j - 1]);
        }
    }
}

void solve(){
    fill_dp();
    std::cout << dp[lx][ly] << std::endl;
    return;
}

int main(){
    std::cin >> q;
    
    for(int i = 0; i < q; ++i){
        std::cin >> sx >> sy;
        lx = sx.size(), ly = sy.size();
        solve();
    }
    return 0;
}