Go: package main

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

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 500001), 500000)
	return scanner
}

func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}

func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}

func main() {
	fp := os.Stdin
	if len(os.Args) > 1 {
		fp, _ = os.Open(os.Args[1])
	}

	scanner := getScanner(fp)
	writer := bufio.NewWriter(os.Stdout)

	n := getNextInt(scanner)
	for i := 0; i < n; i++ {
		x := getNextString(scanner)
		y := getNextString(scanner)

		fmt.Fprintln(writer, lcs(x, y))
	}

	writer.Flush()
}

func lcs(x, y string) int {
	lx := len(x)
	ly := len(y)
	dp := make([][]int, lx+1)
	for i := 0; i <= lx; i++ {
		dp[i] = make([]int, ly+1)
	}
	for i := 0; i < lx; i++ {
		for ii := 0; ii < ly; ii++ {
			if x[i] == y[ii] {
				dp[i+1][ii+1] = dp[i][ii] + 1
				continue
			}
			dp[i+1][ii+1] = dp[i][ii+1]
			if dp[i+1][ii] > dp[i+1][ii+1] {
				dp[i+1][ii+1] = dp[i+1][ii]
			}
		}
	}
	return dp[lx][ly]
}

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

using namespace std;

int q;
int main() {
	cin >> q;
	for (int i = 0; i < q; i++) {
		string x, y;
		cin >> x >> y;
		int m = x.size();
		int n = y.size();
		x = ' ' + x;
		y = ' ' + y;
		int maxl = 0;
		int c[1001][1001] = {};
		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][j - 1], c[i - 1][j]);
				}
			}
		}
		cout << c[m][n] << endl;
	}
	return 0;
}

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


int main(int argc, char *argv[]){
  int n;
  cin >> n;
  for (int r = 0; r < n; r++) {

    string x, y;
    cin >> x >> y;
    int dp[y.length() + 1][x.length() + 1];
    memset(dp, 0, sizeof(dp));
    for (int i = 0; i < y.length(); i++) {
      for (int j = 0; j < x.length(); j++) {
        if(y[i] == x[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]);
        }
      }
    }
    cout << dp[y.length()][x.length()] << endl;
  }
  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define int long long
using ll=long long;
using vi=vector<int>;
using vl=vector<long long>;
using pii=pair<int,int>;
using pll=pair<long long,long long>;
#define ITR(i,c) for(auto i=begin(c);i!=end(c);++i)
#define FORE(x,c) for(auto &x:c)
#define REPF(i,a,n) for(int i=a,i##len=(int)(n);i<i##len;++i)
#define REP(i,n) REPF(i,0,n)
#define REPR(i,n) for(int i=(int)(n);i>=0;--i)
#define REPW(i,n) for(i=0;i<(int)(n);++i)
#define ALL(c) begin(c),end(c)
#define RALL(c) rbegin(c),rend(c)
#define SZ(c) ((int)c.size())
#define CONTAIN(c,x) (c.find(x)!=end(c))
#define OUTOFRANGE(y,x,h,w) (y<0||x<0||y>=h||x>=w)
#define dump(...)
const int DX[9]={0,1,0,-1,1,1,-1,-1,0},DY[9]={-1,0,1,0,-1,1,1,-1,0};
#define INF (1001001001)
#define INFLL (1001001001001001001ll)
template<class T> ostream& operator << (ostream &os,const vector<T> &v) {
    ITR(i,v) os << *i << (i==end(v)-1 ? "" : "\n"); return os; }
template<class T> istream& operator >> (istream &is,vector<T> &v) {
    ITR(i,v) is >> *i; return is; }
template<class T> istream& operator >> (istream &is, pair<T,T> &p) {
        is >> p.first >> p.second; return is; }
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;}
//------------------------------------------------------------------------------
struct before_main_function {
    before_main_function() {
        #ifdef int
            #undef INF
            #define INF INFLL
            #define stoi stoll
        #endif
        cin.tie(0);ios::sync_with_stdio(false);
        cout<<setprecision(15)<<fixed;
        #define endl "\n"
    }
} before_main_function;
//------------------8<------------------------------------8<--------------------

int lcs(string a,string b) {
    int n=a.size(),m=b.size();
    vector<vector<int>> dp(n+1,vector<int>(m+1,0));
    for(int i=0;i<n;i++) {
        for(int j=0;j<m;j++) {
            if(a[i]==b[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]);
            }
        }
    }
    return dp[n][m];
}
signed main() {
    int q;
    cin>>q;
    while(q--) {
        string x,y;
        cin>>x>>y;
        cout<<lcs(x,y)<<endl;
    }
    return 0;
}

C++: import java.io.*;
import static java.lang.Math.max;
import static java.lang.Integer.parseInt;

class Main {
   final static PrintWriter out = new PrintWriter( System.out );

   final static BufferedReader in =
         new BufferedReader( new InputStreamReader( System.in ) );

   final static StringBuilder sb = new StringBuilder("");

   static int lcs(char[] a, char[] b){
      final int alen = a.length;
      final int blen = b.length;
      int dp[][] = new int[alen+1][blen+1];

      for(int i=0; i<alen; ++i){
         for(int j=0; j<blen; ++j){
            if(a[i] == b[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] );
         }
      }
      return( dp[alen][blen] );
   }

   public static void main(String[] args) throws IOException {
      final int N = parseInt( in.readLine() );
      for(int i=0; i<N; ++i){
         char[] a = in.readLine().toCharArray();
         char[] b = in.readLine().toCharArray();
         sb.append( lcs(a,b) );
         sb.append('\n');
      }
      System.out.print(sb);
   }
}

C++: #include <iostream>
#include <string>
using namespace std;
int main(void){
    int n;
    cin >> n;
    for(int i = 0;i < n;i++){
        string X,Y;
        cin >> X >> Y;
        int L[X.length()+10][Y.length()+10];
        for(int j = 0;j < X.length()+10;j++){
            for(int k = 0;k < X.length()+10;k++){
                L[j][k] = 0;
            }
        }
        for(int j = 1;j<=X.length();j++){
            for(int k = 1;k<=Y.length();k++){
                if(Y[k] == X[j]){
                    L[j][k] = 1+L[j-1][k-1];
                }
                else{
                    L[j][k] = max(L[j-1][k],L[j][k-1]);
                }
            }
        }
        cout << L[X.length()][Y.length()] << endl;
    }
return 0;
}

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

int dp[1001][1001];

int lcs(string x, string y)
{
	fill(dp[0], dp[0] + x.length() * y.length(), 0);
	for (int i = 0; i < x.length(); ++i)
	{
		for (int j = 0; j < y.length(); ++j)
		{
			if (x[i] == y[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]);
		}
	}
	return dp[x.length()][y.length()];
}

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++: #define _CRT_SECURE_NO_WARNINGS

#include<iostream>
#include<functional>
#include<algorithm>
#include<stack>
#include<queue>
#include<iomanip>
#include<set>
#include<map>
#include<utility>
#include<string>
#include<vector>

using namespace std;

#define LL long long

string X,Y;
int q,Z;
int dp[1001][1001]={};

int main() {
	cin>>q;
	for(int ds=0;ds<q;ds++){
		cin>>X>>Y;
		int xs=X.size(),ys=Y.size();
		for(int i=0;i<xs;i++){
			for(int j=0;j<ys;j++){
				int tmp=0;
				if(X[i]==Y[j]){
					if(i*j==0)dp[i][j]=1;
					else dp[i][j]=dp[i-1][j-1]+1;
				}
				else {
					if(i+j==0)dp[0][0]=0;
					else if(i==0)dp[0][j]=dp[0][j-1];
					else if(j==0)dp[i][0]=dp[i-1][0];
					else dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
				}
			}
		}
		cout<<dp[xs-1][ys-1]<<endl;
	}
	return 0;
}