Go: package main

/*
最長共通部分列
*/

import (
	"bufio"
	"bytes"
	"fmt"
	"log"
	"os"
	"strconv"
	"strings"
)

func larger(l, r int) int {
	if l > r {
		return l
	}
	return r
}

var memo [1001][1001]int

func countLCS(x, y string) int {
	x = " " + x
	y = " " + y
	max := 0
	for xi := 1; xi < len(x); xi++ {
		for yi := 1; yi < len(y); yi++ {
			if x[xi] == y[yi] {
				memo[xi][yi] = memo[xi-1][yi-1] + 1
			} else {
				memo[xi][yi] = larger(memo[xi-1][yi], memo[xi][yi-1])
			}
			max = larger(max, memo[xi][yi])
		}
	}
	return max
}

func main() {
	scanner := makeScanner(1024)
	q := eGetInt(scanner)
	for i := 0; i < q; i++ {
		x := eGetLine(scanner)
		y := eGetLine(scanner)
		fmt.Println(countLCS(x, y))
	}
}

////////////////////////////////////////////////////////////////////////////////
// ライブラリ
////////////////////////////////////////////////////////////////////////////////
func makeScanner(maxByte int) *bufio.Scanner {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Buffer(make([]uint8, 0, 8192), maxByte)
	return scanner
}
func makeWordScanner() *bufio.Scanner {
	scanner := makeScanner(8192)
	scanner.Split(bufio.ScanWords)
	return scanner
}
func eGetLine(r *bufio.Scanner) string {
	if r.Scan() {
		return r.Text()
	}
	err := r.Err()
	if err != nil {
		log.Fatal(err)
	}
	// EOF
	return ""
}
func eGetInt(r *bufio.Scanner) int {
	line := eGetLine(r)
	return eAtoi(line)
}
func eGetFields(r *bufio.Scanner) []string {
	line := eGetLine(r)
	return strings.Fields(line)
}
func eGetInts(r *bufio.Scanner) []int {
	fields := eGetFields(r)
	ints := make([]int, len(fields))
	for i := 0; i < len(ints); i++ {
		ints[i] = eAtoi(fields[i])
	}
	return ints
}
func eGetChars(r *bufio.Scanner) []string {
	line := eGetLine(r)
	return strings.Split(line, "")
}
func eAtoi(s string) int {
	n, err := strconv.Atoi(s)
	if err != nil {
		log.Fatal(err)
	}
	return n
}

type ints []int

func (s ints) String() string {
	var buf bytes.Buffer
	buf.WriteString("[")
	sep := ""
	for _, v := range s {
		buf.WriteString(fmt.Sprintf("%s%d", sep, v))
		sep = ", "
	}
	buf.WriteString("]")
	return buf.String()
}

func reverse(a ints) ints {
	r := make(ints, len(a))
	for i := 0; i < len(a); i++ {
		r[i] = a[len(a)-1-i]
	}
	return r
}
func max(a ints) (int, bool) {
	if len(a) == 0 {
		return 0, false
	}
	m := a[0]
	for _, e := range a {
		if e > m {
			m = e
		}
	}
	return m, true
}
func min(a []int) int {
	m := a[0]
	for _, v := range a {
		if v < m {
			m = v
		}
	}
	return m
}

func sum(a ints) int {
	if len(a) == 0 {
		return 0
	}
	sum := 0
	for _, e := range a {
		sum += e
	}
	return sum
}
func find(n int, a ints) int {
	for i, v := range a {
		if n == v {
			return i
		}
	}
	return -1
}

C++: #include <iostream>

//include
//------------------------------------------
#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <tuple>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>

using namespace std;

//conversion
//------------------------------------------
inline int toInt(string s)
{
    int v;
    istringstream sin(s);
    sin >> v;
    return v;
}
template <class T>
inline string toString(T x)
{
    ostringstream sout;
    sout << x;
    return sout.str();
}

//math
//-------------------------------------------
template <class T>
inline T sqr(T x) { return x * x; }

//typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<long long> VL;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

//container util
//------------------------------------------
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i, c) for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())

//repetition
//------------------------------------------
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR(i, 0, n)

//constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI = acos(-1.0);

//clear memory
#define CLR(a) memset((a), 0, sizeof(a))

//debug
// #define dump(x) cerr << #x << " = " << (x) << endl;
// #define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" \
//                       << " " << __FILE__ << endl;

class LCS_Solver
{
    vector<VL> vl;
    string &s1;
    string &s2;

public:
    LCS_Solver(size_t s, string &s1, string &s2)
        : vl(s, VL(s, -1)), s1(s1), s2(s2)
    {
        vl[0][0] = 0;
        REP(i, s)
        {
            vl[0][i] = 0;
            vl[i][0] = 0;
        }
    }

    LL solve_memoize(int s1n, int s2m);
    LL solve_dp(int s1n, int s2m) const;
};

LL LCS_Solver::solve_memoize(int s1n, int s2m)
{
    // cout << s1n << ", " << s2m << endl;
    if (vl[s1n][s2m] >= 0)
    {
        return vl[s1n][s2m];
    }
    else
    {
        LL ans;
        if (s1[s1n - 1] == s2[s2m - 1])
        {
            ans =
                solve_memoize(s1n - 1, s2m - 1) + 1;
            vl[s1n][s2m] = ans;
            return ans;
        }
        else
        {
            ans = max(
                solve_memoize(s1n - 1, s2m),
                solve_memoize(s1n, s2m - 1));
            vl[s1n][s2m] = ans;
            return ans;
        }
    }
}

const size_t MAX_SIZE = 2000;

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

    LL ans;
    REP(_, n)
    {
        string s1, s2;
        cin >> s1;
        cin >> s2;
        // cout << s1.size() << " " << s2.size() << endl;

        ans = LCS_Solver(MAX_SIZE, s1, s2)
                  .solve_memoize(s1.size(), s2.size());
        cout << ans << endl;
    }
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define  all(x) (x).begin(),(x).end()
typedef long long ll;

int c[1005][1005];

int lcs(string s1, string s2){
    int n = s1.size();
    int m = s2.size();
    s1 = " " + s1;
    s2 = " " + s2;
    for(int i = 0; i <= n; i++) c[i][0] = 0;
    for(int i = 0; i <= n; i++) c[0][i] = 0;

    int ans = 0;
    for (int i1 = 1; i1 <= n; i1++){
        for(int i2 = 1; i2 <= m; i2++){
            if(s1[i1] == s2[i2]){
                c[i1][i2] = c[i1-1][i2-1] + 1;
            }else{
                c[i1][i2] = max(c[i1-1][i2], c[i1][i2-1]);
            }
        }
        ans = max(ans, c[i1][m]);
    }
    return ans;
}

int main(){
    int q;
    cin >> q;
    vector<int> ans(q);
    for(int i = 0; i < q; i++){
        string s1, s2;
        cin >> s1 >> s2;
        ans[i] = lcs(s1, s2);
    }
    rep(i,q) cout << ans[i] << endl;
    return 0;
}