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 <cstdint>
#include <string>
#include <utility>

using namespace std;

#define MAX_LEN 1001
static size_t memo[MAX_LEN][MAX_LEN];

size_t lcs(string &a, string &b)
{
  for (uint32_t i = 0; i <= a.size(); i++) {
    memo[i][0] = 0;
  }

  for (uint32_t i = 0; i <= b.size(); i++) {
    memo[0][i] = 0;
  }

  for (uint32_t i = 1; i <= a.size(); i++) {
    for (uint32_t j = 1; j <= b.size(); j++) {
      if (a[i - 1] == b[j - 1]) {
        memo[i][j] = memo[i - 1][j - 1] + 1;
      } else {
        memo[i][j] = max(memo[i - 1][j], memo[i][j - 1]);
      }
    }
  }

  return memo[a.size()][b.size()];
}

#include <iostream>

int32_t main()
{
  uint32_t num;
  cin >> num;

  for (uint32_t i = 0; i < num; i++) {
    string a, b;
    cin >> a;
    cin >> b;
    cout << lcs(a, b) << endl;
  }

  return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <utility>
#include <vector>
#include <string>
#include <queue>
#include <tuple>
#include <cmath>
#include <map>
#include <bitset>
#define _overload3(_1,_2,_3,name,...) name
#define _rep(i,n) repi(i,0,n)
#define repi(i,a,b) for(ll i=ll(a);i<ll(b);++i)
#define rep(...) _overload3(__VA_ARGS__,repi,_rep,)(__VA_ARGS__)
#define all(x) (x).begin(),(x).end()
#define PRINT(V) cout << V << "\n"
#define SORT(V) sort((V).begin(),(V).end())
#define RSORT(V) sort((V).rbegin(), (V).rend())
using namespace std;
using ll = long long;
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; }
inline void Yes(bool condition){ if(condition) PRINT("Yes"); else PRINT("No"); }
template<class itr> void cins(itr first,itr last){
    for (auto i = first;i != last;i++){
        cin >> (*i);
    }
}
template<class itr> void array_output(itr start,itr goal){
    string ans = "";
    for (auto i = start;i != goal;i++) ans += to_string(*i)+" ";
    if (!ans.empty()) ans.pop_back();
    PRINT(ans);
}
constexpr const ll INF = 1e15;
constexpr const ll MOD = 1000000007;
constexpr const ll MAX = 15;
constexpr int nx[4] = {1,0,-1,0};
constexpr int ny[4] = {0,1,0,-1};
typedef pair<ll,ll> P;
ll LCA(string x,string y){
    ll a = x.length();
    ll b = y.length();
    vector<vector<ll>> dp(a+1,vector<ll>(b+1,0));
    rep(i,a){
        rep(j,b){
            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[a][b];
}
int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll q;
    cin >> q;
    rep(i,q){
        string x,y;
        cin >> x >> y;
        PRINT(LCA(x,y));
    }
}

C++: #include <bits/stdc++.h>
/*
#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <cstring>
#include <complex>
#include <stack>
#include <queue>
#include <unordered_map>
#include <map>
 */
#define INF 10e9
#define rep(i, a) for (int i = 0; i < (a); i++)
using namespace std;
 
int main() {
    int dp[1010][1010];

    int q;
    cin >> q;

    string x, y;

    int i, j, k;
    for(k = 0; k < q; k++){
        cin >> x >> y;
        dp[0][0] = 0;
        dp[0][1] = 0;
        dp[1][0] = 0;

        for(i = 1; i <= x.size(); i++){
            for(j = 1; j <= y.size(); j++){
                if(x[i-1] == y[j-1]){
                    dp[i][j] = dp[i-1][j-1] + 1;
                }else{
                    dp[i][j] = max(dp[i][j-1], dp[i-1][j]);
                }
            }
        }

        cout << dp[x.size()][y.size()] << endl;
    }
}

C++: #include <iostream>
#include <algorithm>
#include <string>
using namespace std;
int LCS(string X,string Y){
    int cnt=-1;
    int c[1001][1001];
    int m=X.size();
    int n=Y.size();
    X=' '+X;
    Y=' '+Y;
    for(int i=1;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][j-1],c[i-1][j]);
            }
            cnt=max(cnt,c[i][j]);
        }
    }
    return cnt;
}
int main(){
    int n;
    string X,Y;
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>X>>Y;
        cout<<LCS(X,Y)<<endl;
    }
    return 0;
}

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

void fnInput(vector<string>& rvsStrX, vector<string>& rvsStrY)
{
  int nMaxSiz;
  cin >> nMaxSiz;
  rvsStrX.resize(nMaxSiz);
  rvsStrY.resize(nMaxSiz);

  for (int i = 0; i < nMaxSiz; ++i)
  {
    cin >> rvsStrX[i] >> rvsStrY[i];
    rvsStrX[i] = ' ' + rvsStrX[i];
    rvsStrY[i] = ' ' + rvsStrY[i];
  }
}

int fnLngCmnSubseq(const vector<string>& cnrvsStrX, const vector<string>& cnrvsStrY)
{
  vector<vector<int>> vvnLcsDP;
  for (int i = 0; i < cnrvsStrX.size(); ++i)
  {
    const int nMAXNX = cnrvsStrX[i].size();
    const int nMAXNY = cnrvsStrY[i].size();

    vvnLcsDP.clear();
    vvnLcsDP.resize(nMAXNX, vector<int>(nMAXNY, 0));

    for (int nx = 1; nx < nMAXNX; ++nx)
      for (int ny = 1; ny < nMAXNY; ++ny)
        if (cnrvsStrX[i][nx] == cnrvsStrY[i][ny])
          vvnLcsDP[nx][ny] = vvnLcsDP[nx - 1][ny - 1] + 1;
        else
          vvnLcsDP[nx][ny] = max(vvnLcsDP[nx - 1][ny], vvnLcsDP[nx][ny - 1]);

    cout << vvnLcsDP[nMAXNX - 1][nMAXNY - 1] << endl;
  }
}

int main()
{
  cin.tie(0);
  ios::sync_with_stdio(false);
  vector<string> vsStrX, vsStrY;

  fnInput(vsStrX, vsStrY);
  fnLngCmnSubseq(vsStrX, vsStrY);
  return 0;
}