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<stdio.h>
#include<string>
#include<algorithm>
using namespace std;

int lcs(string X, string Y) {
    int c[1001][1001];
    int m = X.size();
    int n = Y.size();
    X = ' ' + X;
    Y = ' ' + Y;
    int maxl = 0;
    for (int i = 0; i < m + 1; i++) c[i][0] = 0;
    for (int j = 1; j < n + 1; j++) c[0][j] = 0;
    
    for (int i = 1; i < m + 1; i++) {
        for (int j = 1; j < n + 1; 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]);
            }
            maxl = max(maxl, c[i][j]);
        }
    }
    return maxl;
}

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<string>
#include<algorithm>
using namespace std;
static const int N = 1000;

int lcs(string X, string Y){
	int c[N + 1][N + 1];
	int m = X.size();
	int n = Y.size();
	int maxl = 0;
	X = ' ' + X;
	Y = ' ' + Y;
	for(int i=1;i<=m;i++) c[i][0] = 0;
	for(int j=1;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]);
			}
			maxl = max(maxl,c[i][j]);
		}
	}

	return maxl;
}

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 REP(i, t, n)  for (int i = t; i < n; i++)
#define ALL(n)        (n).begin(),(n).end()
#include <limits.h>
#include <stdio.h>
#include <cmath>
#include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <map>
#include <queue>
#include <deque>
#include <functional>
#include <algorithm>
#include <cstring>
#include <unordered_map>
#include <numeric>

using namespace std;

typedef bool               BOOL;
typedef short              WORD;
typedef unsigned short     U_WORD;
typedef long               DWORD;
typedef unsigned long      U_DWORD;
typedef long long          QWORD;
typedef unsigned long long U_QWORD;

#define LEN_MAX (1000)
DWORD dpLCS[LEN_MAX + 1][LEN_MAX + 1];

void initDpTable(DWORD maxI, DWORD maxJ)
{
	REP(i, 0, maxI + 1) {
		REP(j, 0, maxJ + 1) {
			dpLCS[i][j] = 0;
		}
	}

}

void solve_main()
{
	DWORD dwNum;
	string str1, str2;
	cin >> dwNum;
	REP(loop, 0, dwNum) {
		cin >> str1;
		cin >> str2;
		initDpTable(str1.length(), str2.length());

		REP(i, 1, (str1.length() + 1)) {
			REP(j, 1, (str2.length() + 1)) {
				if (str1[i - 1] == str2[j - 1]) {
					dpLCS[i][j] = dpLCS[i - 1] [j - 1] + 1;
				} else {
					dpLCS[i][j] = max(dpLCS[i - 1][j], dpLCS[i][j - 1]);
				}
			}
		}
		cout << dpLCS[str1.length()][str2.length()] << endl;
	}
}

int main()
{
#ifdef FOR_IDE
	ifstream in("input.txt");
	cin.rdbuf(in.rdbuf());
#endif

	solve_main();
	return 0;
}

C++: //   _/                _/                 _/_/_/   _/
//_/_/_/_/   _/_/   _/_/_/_/   _/_/    _/       _/_/
// _/     _/    _/   _/     _/    _/  _/_/_/     _/
//_/     _/    _/   _/     _/    _/  _/    _/   _/
// _/_/   _/_/       _/_/   _/_/      _/_/     _/
#include<iostream>
#include<algorithm>
#include<cmath>
#include<iomanip>
#include<set>
#include<map>
#include<queue>
#include<vector>
#include<random>
using namespace std;
typedef long long ll;
const int MOD=1e9+7;
const double pi=3.14159265358979323846;
const int inf=1e9;
const ll INF=1e18;
int main() {
  cin.tie(0),cout.tie(0);
  ios::sync_with_stdio(false);
  int q;
  cin >> q;
  while(q--) {
    string s,t;
    cin >> s >> t;
    int dp[s.size()+5][t.size()+5]={};
    for(int i=1; i<=s.size(); i++) {
      for(int j=1; j<=t.size(); 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[s.size()][t.size()] << endl;
  }
 }

C++: #include <iostream>
#include <string>
using namespace std;
static const int MAX = 1001;

void lcs(string X, string Y) {
	int dp[MAX][MAX];  
	int i,j;

	int xLength = X.size();
	int yLength = Y.size();


	// initialize dp[][]
	for (i = 1; i <= xLength; i++)
		dp[i][0] = 0;
	for (i = 1; i <= yLength; i++)
		dp[0][i] = 0;

	for (i = 1; i <= xLength; i++){
		for (j = 1; j <= yLength; j++){
			// Because the original string is 0-based , so subtracted from 1
			if (X[i - 1] == Y[j - 1]) {
				dp[i][j] = dp[i-1][j-1] + 1;
			}else {
				dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
			}
		}
	}

	// testing code: print out the dp[][]
	cout << "j";
	for (j = 1; j <= yLength; j++)
		cout << ' ' << j ;
	cout << endl;
		

	for (i = 1; i <= xLength; i++){
		cout << i << '.';
		for (j = 1; j <= yLength; j++){
			cout << dp[i][j] << ' ';
		}
		cout << endl;
	}

	cout << dp[xLength][yLength] << endl;
}

int main() {
	int n , i;
	string X, Y;

	cin >> n;
	for (i = 0 ; i < n; i++ ) {
		cin >> X;
		cin >> Y;
		lcs(X, Y);
	}

	return 0;

}