Go: package main

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

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

func (s *Scanner) nextStr() string {
	s.sc.Scan()
	return s.sc.Text()
}

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// Main
func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	Q := sc.nextInt()
	for q := 0; q < Q; q++ {
		X, Y := sc.nextStr(), sc.nextStr()
		xLen, yLen := len(X), len(Y)
		dp := make([][]int, xLen+1)
		for i := 0; i <= xLen; i++ {
			dp[i] = make([]int, yLen+1)
		}
		for x := 0; x <= xLen; x++ {
			for y := 0; y <= yLen; y++ {
				if x == 0 || y == 0 {
					dp[x][y] = 0
				} else if X[x-1] == Y[y-1] {
					dp[x][y] = dp[x-1][y-1] + 1
				} else {
					dp[x][y] = max(dp[x-1][y], dp[x][y-1])
				}
			}
		}
		fmt.Fprintln(wtr, dp[xLen][yLen])
	}

	wtr.Flush()
}

C++: #include<iostream>
#include<algorithm>
using namespace std;
int dp[1001][1001];
string s,t;
int n,m,a,ans;
int main(){
  cin>>a;
  for(int k=0;k<a;k++){
    cin>>s>>t;
    for(int i=0;i<=1000;i++)
      for(int j=0;j<=1000;j++)
    dp[i][j]=0;
    m=s.size();
    n=t.size();
    ans=0;
    for(int i=1;i<=m;i++){
      for(int j=1;j<=n;j++){
    if(s[i-1]==t[j-1]){
      dp[i][j]=dp[i-1][j-1]+1;
    }else{
      dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
    }
      }
    } 
    cout<<dp[m][n]<<endl;
  }
  return 0;
}

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

int lcs(string x, string y) {
	int m = x.size();
	int n = y.size();
	//cout<<m<<n<<endl;
	int maxl = 0;
	int A[1001][1001]={};
	x = ' ' + x;
	y = ' ' + y;
//	cout<<x<<y;
	for (int i = 0;i <= m;i++) {
		A[i][0] = 0;
	}
	for (int j = 0;j <= n;j++) {
		A[0][j] = 0;
	}

	for (int i = 1;i <= m;i++) {
		for (int j = 1;j <= n;j++) {
		//	cout<<x[i]<<y[j]<<endl;
			if (x[i] == y[j]) {
					A[i][j] = A[i-1][j-1] + 1;
			}
	     	else {
					A[i][j] = max(A[i - 1][j], A[i][j - 1]);
			}

			maxl = max(maxl, A[i][j]);
		}
		
	}
	return maxl;
}

int main() {
	int n;
	string x, y;
	cin >> n;
	for (int i = 0;i < n;i++) {
		cin >> x >> y;
		cout<<lcs(x, y)<<endl;
		//lcs(x,y);

	}
	return 0;
}

C++: #ifdef LOCAL_BUILD
#include "pch.h"
#define DLOG(msg) cout << "#" << __LINE__ << ":" << msg << endl;
#define DLOG_V(var)\
  cout << "#" << __LINE__ << ":" << #var << " : " << var << endl;
#else
#include <bits/stdc++.h>
#define DLOG(msg)
#define DLOG_V(var)
#endif
using namespace std;

constexpr auto no_value = numeric_limits<uint64_t>::max();

int solve(const string& str1, const string& str2) {
  int max_ = 0;
  vector<vector<int>> buf(str1.size(), vector<int>(str2.size(), 0));
  for (size_t j = 0; j < str2.size(); ++j) {
    for (size_t i = 0; i < str1.size(); ++i) {
      auto prev1 = j == 0 ? 0 : buf[i][j - 1];
      auto prev2 = i == 0 ? 0 : buf[i - 1][j];
      buf[i][j] = max(prev1, prev2);
      if (str1[i] == str2[j]) {
        auto p = i == 0 || j == 0 ? 0 : buf[i - 1][j - 1];
        buf[i][j] = max(buf[i][j], p + 1);
        max_ = max(max_, buf[i][j]);
      }
    }
  }
  return max_;
}

int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; ++i) {
    string str1;
    string str2;
    cin >> str1 >> str2;
    auto res = solve(str1, str2);
    cout << res << endl;
  }
}

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

int lcs(string s,string t)
{
  int c[1005][1005];
  int m=s.size(),n=t.size(),len=0;

  for(int i=0;i<=m;i++) c[i][0]=0;
  for(int i=0;i<=n;i++) c[0][i]=0;


  for(int i=1;i<=m;i++)
  {
    for(int j=1;j<=n;j++)
    {
      if(s.at(i-1)==t.at(j-1)) c[i][j]=c[i-1][j-1]+1;
      else c[i][j]=max(c[i-1][j],c[i][j-1]);

      len=max(len,c[i][j]);
    }
  }

  return len;
}

int main()
{
  int q;
  cin>>q;
  string s,t;
  for(int i=0;i<q;i++)
  {
    cin>>s>>t;
    cout<<lcs(s,t)<<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 LMAX=0;
  int m=X.size(), n=Y.size();

  X=' ' + X;
  Y=' ' + Y;

  for(int i=0; i<=m; i++) c[i][0]=0;
  for(int j=0; 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]);
      }
      LMAX=max(LMAX, c[i][j]);
    }
  }

  return LMAX;
}

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 <algorithm>
#include <vector>
#include <deque>
#include <queue>
#include <list>
#include <stack>
#include <string>
#include <tuple>
#include <functional>
#include <numeric>
#include <cmath>
#include <iomanip>
#include <map>
#include <random>
#include <cstdlib>
#define Loop(i, n) for(int i = 0; i < (int)n; i++)
#define Loop1(i, n) for(int i = 1; i <= (int)n; i++)
#define Loopr(i, n) for(int i = (int)n - 1; i >= 0; i--)
#define Loopr1(i, n) for(int i = (int)n; i >= 1; i--)
using namespace std;
typedef long long int ll;
 
string x, y;
int memo[1005][1005];
 
int dp(int a, int b) {
    if (memo[a][b] != INT_MIN) return memo[a][b];
    if (a == 0 || b == 0) memo[a][b] = 0;
    else if (x[a - 1] == y[b - 1]) {
        memo[a][b] = dp(a - 1, b - 1) + 1;
    }
    else {
        memo[a][b] = max(dp(a - 1, b), dp(a, b - 1));
    }
    return memo[a][b];
}
 
int main() {
    int q;
    cin >> q;
    Loop(i, q) {
        cin >> x >> y;
        Loop(j, x.size()+1) {
            Loop(k, y.size()+1) {
                memo[j][k] = INT_MIN;
            }
        }
        cout << dp(x.size(), y.size()) << endl;
    }
    return 0;
}

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

string S,T;
int x[10000],y[10000];
int dp[10000][10000];
char U[27]="abcdefghijklmnopqrstuvwxyz";
int MAXN;

int main(){
	int q;
	cin>>q;
	for(int i=0;i<q;i++){
		MAXN=0;
		cin>>S>>T;
		for(int i=0;i<S.size();i++){
			for(int j=0;j<26;j++){
				if(S[i]==U[j]){
					x[i+1]=j;
				}
			}
		}
		for(int i=0;i<T.size();i++){
			for(int j=0;j<26;j++){
				if(T[i]==U[j]){
					y[i+1]=j;
				}
			}
		}
		for(int i=0;i<=T.size();i++){
			for(int j=0;j<=S.size();j++){
				if(i==0 || j==0){
					dp[i][j]=0;
				}
				else if(x[j]==y[i]){
					dp[i][j]=dp[i-1][j-1]+1;
				}
				else{
					dp[i][j]=max(dp[i][j-1],dp[i-1][j]);
				}
			}
		}
		for(int i=0;i<=T.size();i++){
			for(int j=0;j<=S.size();j++){
				MAXN=max(MAXN,dp[i][j]);
			}
		}
		cout<<MAXN<<endl;
	}
	return 0;
}