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 <vector>
#include <string>

using namespace std;

// 多次元配列の初期化方法確認
// 出力確認
//
void traceback (string x, string y, vector<vector<int>> L) {
	string lcs;
	int i = x.length();
	int j = y.length();
	while(i != 0 && j != 0) {
		if (L[i][j] == L[i-1][j-1] + 1) {
			lcs = x[i-1] + lcs;
			i--;
			j--;
		} else if (L[i][j-1] >= L[i-1][j]) {
			j--;
		} else if (L[i][j-1] <= L[i-1][j]) {
			i--;
		}
	}
	
	cout << lcs << endl;
}

int main(void) {
	int q;
	cin >> q;
	string x, y;
	
	while(q--) {
		cin >> x >> y;

	//	vector<vector<int>> L(max(x.length(), y.length()), 0);
		vector<vector<int>> L(x.length() + 1, vector<int>(y.length() + 1, 0));
		for (int i = 0; i <= x.length(); i++) {
			for (int j = 0; j <= y.length(); j++) {
				if (i == 0 || j == 0) L[i][j] = 0;
				else if (x[i-1] == y[j-1]) {
					L[i][j] = L[i-1][j-1] + 1;
				} else if (x[i-1] != y[j-1]) {
					L[i][j] = max(L[i-1][j], L[i][j-1]);
				}
			}
		}
		//出力がよくない状況
		cout << L[x.length()][y.length()] << endl;

		//traceback(x, y, L);
	}

}
// xi = yj
// Lij = Li-1j-1 + 1
// Lij = max(Li-1j, Lij-1)

C++: #include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)



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

int main() {
	int q;
  	cin >>q;
  	rep(k,q){
    	string x,y;
    	cin >>x>>y;
      	cout <<lcs(x,y)<<endl;
      	
    }  
}

C++: #include <bits/stdc++.h>

using namespace std;
typedef long long int ll;
typedef pair<int, int> P;
typedef pair<ll, ll> Pll;
typedef vector<int> Vi;
typedef tuple<int, int, int> T;
#define FOR(i,s,x) for(int i=s;i<(int)(x);i++)
#define REP(i,x) FOR(i,0,x)
#define ALL(c) c.begin(), c.end()
#define DUMP( x ) cerr << #x << " = " << ( x ) << endl

int dp[2][1024];

int main() {
  // use scanf in CodeForces!
  cin.tie(0);
  ios_base::sync_with_stdio(false);

  int N;
  cin >> N;
  REP(q, N) {
    string X, Y;
    cin >> X >> Y;
    int LX = X.size(), LY = Y.size();
    REP(i, 2) REP(j, LY+1) dp[i][j] = 0;
    REP(i, LX) REP(j, LY) {
      if (X[i] == Y[j]) {
	dp[(i+1)%2][j+1] = max(dp[i%2][j] + 1, max(dp[(i+1)%2][j], dp[i%2][j+1]));
      } else {
	dp[(i+1)%2][j+1] = max(dp[(i+1)%2][j], dp[i%2][j+1]);
      }
    }
    cout << dp[LX%2][LY] << endl;
  }
  return 0;
}

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

#define REP(i, n) for(int (i) = 0; (i) < (n); (i)++)

string str1, str2;
int dp[1001][1001];

void solve()
{
  REP(i, str1.size())
    if(str1[i] == str2[str2.size() - 1])
      dp[i][str2.size() - 1] = 1;
    else
      dp[i][str2.size() - 1] = 0;
  for(int i = str2.size() - 2; i >= 0; i--)
    if(str1[str1.size() - 1] == str2[i])
      dp[str1.size() - 1][i] = 1;
    else
      dp[str1.size() - 1][i] = dp[str1.size() - 1][i + 1];
  for(int i = str1.size() - 2; i >= 0; i--){
    for(int j = str2.size() - 2; j >= 0; j--){
      if(str1[i] == str2[j])
	dp[i][j] = dp[i + 1][j + 1] + 1;
      else
	dp[i][j] = max(dp[i + 1][j], dp[i][j + 1]);
    }
  }
}
  
int main()
{
  int q, m = 0;
  cin >> q;
  cin.ignore();
  REP(i, q){
    getline(cin, str1);
    getline(cin, str2);
    fill(&dp[0][0], &dp[1001][0], -1);
    solve();
    REP(i, str1.size())
      m = (dp[i][0] > m) ? dp[i][0] : m; 
    cout << m << endl;
  }
}

C++: #include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<algorithm>
#include<bitset>
#include<vector>
#include<deque>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<cmath>
#include<iomanip>
#include <functional>
using namespace std;
typedef long long ll;
const int mod = 1000000007;
const int INF = 1 << 28;
//cout << fixed << std::setprecision(9)
//memset(a, 0, sizeof(a));
//--------------------------

int lcs(string x, string y)
{
	x = " " + x;
	y = " " + y;
	int n = x.size();
	int m = y.size();

	int dp[1100][1100];
	memset(dp, 0, sizeof(dp));

	for (int i = 0; i <= n; i++)
		for (int j = 0; j <= m; j++) {
			if (i == 0 || j == 0) {
				dp[i][j] = 0;
				continue;
			}
			if (x[i] == y[j]){
				dp[i][j] = dp[i - 1][j - 1] + 1;
			}
			else {
				dp[i][j] = min(dp[i - 1][j], dp[i][j - 1]);
			}
		}
	return dp[n][m];
}

int main()
{
	int q;
	for (int i = 0; i < q; i++) {
		string s1, s2;
		cout << lcs(s1, s2) << endl;
	}

	return 0;
}