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++: // #Sazaの1日1AC
#include <bits/stdc++.h>
using namespace std;
const long long mod = 1000000000 + 7;
const long long INF = 9e18;
const double PI = 3.14159265358979323846;

//マクロ
//型エイリアス
using ll = long long;
using P = pair<long long, long long>;
using vl = vector<long long>;
using vvl = vector<vector<long long>>;
using vP = vector<pair<long long, long long>>;
//ショートカット
#define rep(i, n) for (int i = 0; i < n; i++)
#define rep2(i, k, n) for (int i = k; i < n; i++) //半開区間
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define pb push_back
#define mkp make_pair
//入力
#define vin(v, N) for (long long i = 0; i < N; i++) cin >> v.at(i)
#define lin(n)long long n;cin >> n
#define chin(x)char x;cin >> x;
#define sin(s)string s;cin >> s;
#define vlin(v, N)vector<long long> v(N);for (long long i = 0; i < N; i++)cin >> v.at(i)
#define max(a, b) max((ll)a, (ll)b)
#define min(a, b) min((ll)a, (ll)b)

//関数
//最大公約数
long long gcd(long long m, long long n){
  long long a = max(m, n);
  long long b = min(m, n);
  long long r = a % b;
  while (r != 0){
    a = b;
    b = r;
    r = a % b;
  }
  return b;
}
// 最小公倍数
long long lcd(long long m, long long n){
  return m * n / gcd(m, n);
}
//xのn乗
long long power(long long x, long long N){
  long long ret = 1;
  for (long long i = 0; i < N; i++)
    ret *= x;
  return ret;
}
//繰り返し二乗法
long long repeat_squaring(long long x, long long n){
  if (n == 0)
    return 1;
  else if (n % 2 == 0)
  {
    long long t = repeat_squaring(x, n / 2);
    return t * t % mod;
  }
  else
    return x * repeat_squaring(x, n - 1);
}
//素因数分解(mapで返す)
map<long long, long long> factor(long long p){
  ll p1 = p;
  map<long long, long long> ret;
  for (long long i = 2; i * i <= p1; i++)
  {
    while (p % i == 0)
    {
      ret[i]++;
      p /= i;
    }
  }
  if (p != 1)
    ret[p]++;
  return ret;
}
//素数判定
bool is_prime(long long N){
  for (long long i = 2; i * i <= N; i++)
  {
    if (N % i == 0)
      return false;
  }
  return true;
}
//最大値更新
void chmax(long long &a, long long b){
  a = max(a, b);
}
//最小値更新
void chmin(long long &a, long long b){
  a = min(a, b);
}

//構造体
//Union-Find木
struct UnionFind
{
  //メンバ変数
  vector<long long> par; //par[i]:=頂点iの親
  vector<long long> s;   //s[i]:=頂点iが属する集合の個数(iが根のとき)

  //コンストラクタ
  UnionFind(long long N) : par(N), s(N){
    for (long long i = 0; i < N; i++)
    {
      par[i] = i; //最初はすべてが根として初期化
      s[i] = 1;
    }
  }
  //メンバ関数
  //root(i):=頂点iの根
  long long root(long long i){
    if (par[i] == i)
      return i;
    par[i] = root(par[i]); //経路圧縮
    return root(par[i]);   //再帰
  }
  //size[i]:=iが属する集合の個数
  long long size(long long i){
    return s[root(i)];
  }
  //same(x,y) xとyが同じ根を持つか(同じ集合に含まれるか)
  bool same(long long x, long long y){
    return root(x) == root(y);
  }
  //unite(x,y) xの根をyの根に繋げる(集合を合併)
  void unite(long long x, long long y){
    if (!same(x, y)){
      long long rx = root(x);
      long long ry = root(y);
      par[rx] = par[ry];
      s[ry] = s[rx] + s[ry];
    }
  }
};
//Binary Indexed Tree
struct BIT{
  vector<long long> bit;
  long long N;

  BIT(long long n){
    N = n;
    bit.resize(N + 1);
  }

  void add(long long i, long long w){
    for (long long x = i; x <= N; x += x & -x){
      bit[x] += w;
    }
  }
  long long sum(long long i){
    long long ret = 0;
    for (long long x = i; x > 0; x -= x & -x){
      ret += bit[x];
    }
    return ret;
  }
};
/////////////////⊂('ω'⊂ )))Σ≡GO!/////////////////



int main(){
  //doubleの桁数
  cout << fixed << setprecision(10);

  lin(q);
  rep(hoge, q){
    sin(x); sin(y);
    ll dp[1010][1010];

    ll N = x.size(), M = y.size();
    rep(i,N){
      rep(j,M){
        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]);
      }
    }
    cout << dp[N][M] << endl;
  }

  
}

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

#define FOR( i, m, n )  for( int (i) = (m); (i) < (n); (i)++ )
#define REP( i, n )     FOR( i, 0, n )
#define ALL( a )        (a).begin(), (a).end()             

int	dp[1001][1001] = {};

int main() {
	int n; cin >> n;

	int maxl;

	string s1, s2;
	REP( i, n ) {
		cin >> s1 >> s2;
		s1 = ' ' + s1;
		s2 = ' ' + s2;
		maxl = 0;
		memset( dp, 0, sizeof( int ) );
		FOR( j, 1, s1.size() ) {
			FOR( k, 1, s2.size() ) {
				if( s1[j] == s2[k] ) {
					dp[j][k] = dp[j - 1][k - 1] + 1;
				} else {
					dp[j][k] = max( dp[j - 1][k], dp[j][k - 1] );
				}
				maxl = max( dp[j][k], maxl );
			}
		}

		cout << maxl << endl;
	}
}

C++: #include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define FOR(i, s, e) for (int i = (int)(s); i <= (int)(e); i++)
#define printYesNo(is_ok) puts(is_ok ? "Yes" : "No");
#define SORT(v) sort(v.begin(), v.end());
#define RSORT(v) sort(v.rbegin(), v.rend());
#define REVERSE(v) reverse(v.begin(), v.end());

template <typename T>
void printlnVector(T v)
{
  rep(i, v.size())
  {
    cout << v[i] << endl;
  }
}

template <typename T>
void printVector(T v)
{
  rep(i, v.size())
  {
    cout << v[i] << " ";
  }
  cout << endl;
}

int main()
{
  int q;
  cin >> q;
  rep(Q, q)
  {
    string X, Y;
    cin >> X >> Y;
    vector<vector<int> > dp(X.size(), vector<int>(Y.size()));
    if(X[0]  == Y[0])
      dp[0][0]++;

    rep(i, X.size() - 1)
    {
      if(X[i + 1] == Y[0])
        dp[i + 1][0]++;
      dp[i + 1][0] = max(dp[i + 1][0], dp[i][0]);
    }

    rep(i, Y.size() - 1)
    {
      if(X[0] == Y[i + 1])
        dp[0][i + 1]++;
      dp[0][i + 1] = max(dp[0][i + 1], dp[0][i]);
    }

    rep(i, X.size() - 1) rep(j, Y.size() - 1)
    {
      if(X[i + 1] == Y[j + 1])
        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[X.size() - 1][Y.size() - 1] << endl;
  }
  return 0;
}