Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

func (s *Scanner) nextStr() string {
	s.sc.Scan()
	return s.sc.Text()
}

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// Main
func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	Q := sc.nextInt()
	for q := 0; q < Q; q++ {
		X, Y := sc.nextStr(), sc.nextStr()
		xLen, yLen := len(X), len(Y)
		dp := make([][]int, xLen+1)
		for i := 0; i <= xLen; i++ {
			dp[i] = make([]int, yLen+1)
		}
		for x := 0; x <= xLen; x++ {
			for y := 0; y <= yLen; y++ {
				if x == 0 || y == 0 {
					dp[x][y] = 0
				} else if X[x-1] == Y[y-1] {
					dp[x][y] = dp[x-1][y-1] + 1
				} else {
					dp[x][y] = max(dp[x-1][y], dp[x][y-1])
				}
			}
		}
		fmt.Fprintln(wtr, dp[xLen][yLen])
	}

	wtr.Flush()
}

C++: #include<iostream>
#include<string>
#include<algorithm>

using namespace std;

string  X,Y;
int q;

int do_dp(int ax,int ay){
  int dp[ax][ay] = {};
  
  for(int i = 0;i < ax;i++){
    if(X[i] == Y[0]) dp[i][0] = 1;
    else dp[i][0] = max(dp[i][0],dp[i - 1][0]);
  }
  
  for(int j = 1;j < ay;j++){
    if(X[0] == Y[j]) dp[0][j] = 1;
    else dp[0][j] = max(dp[0][j],dp[0][j - 1]);
  }

  for(int i = 1;i < ax;i++){
    for(int j = 1;j < ay;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]);
      }
    }
  }
  
  /*for(int i = 0;i < ax;i++){
    for(int j = 0;j < ay;j++){
      cout << dp[i][j] << " ";
    }
    cout << '\n';
    }*/
  
  return dp[ax - 1][ay - 1];
}

int main(){
  string str;
  
  cin >> q;
  
  int A[q];
  
  for(int i = 0;i < q;i++){
    cin >> X;
    cin >> Y;
    A[i] = do_dp(X.size(),Y.size());
  }
  
  for(int i = 0;i < q;i++){
    cout << A[i] << '\n';
  }
  
  return 0;
}

C++: #include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

int lcs(string s, string t) {
  int n = s.length();
  int m = t.length();
  s = " " + s;
  t = " " + t;
  // dp[i][j] := sのi文字目, tのj文字目まで見たときの LCS
  vector<vector<int>> dp(n + 1, vector<int>(m + 1, 0));
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      if (s[i] == t[j]) {
        dp[i][j] = dp[i - 1][j - 1] + 1;
      } else {
        dp[i][j] = max(dp[i][j - 1], dp[i - 1][j]);
      }
    }
  }
  return dp[n][m];
}

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

  while (q--) {
    string s, t;
    cin >> s >> t;
    cout << lcs(s, t) << endl;
  }
  return 0;
}

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

static const int N = 1000;

int las(string x, string y) {
int c[N + 1][N + 1];
int m = x.size();
int n = y.size();
int mail = 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 mail;
}

int main() {
string s1, s2;
int n; cin >> n;
for ( int i = 0; i < n; i++ ) {
cin >> s1 >> s2;
cout << les(s1, s2) << endl;
}
return 0;
}

C++: #include <bits/stdc++.h>
#define REP(i, n) for (int i = 0; i < n; i++)
#define FOR(i, m, n) for (int i = m; i < n; i++)
#define ll long long int
const int INF = 2147483647;

using namespace std;

int dp[1001][1001] = {};
int main()
{
  int q;
  cin >> q;
  REP(i, q)
  {
    string x, y;
    cin >> x >> y;

    REP(i, x.length() + 1)
    {
      dp[i][0] = 0;
    }
    REP(j, y.length() + 1)
    {
      dp[0][j] = 0;
    }

    FOR(i, 1, x.length() + 1)
    {
      FOR(j, 1, y.length() + 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 - 1], max(dp[i][j - 1], dp[i - 1][j]));
      }
    }
    cout << dp[x.length()][y.length()] << endl;
  }
}

C++: #define _GLIBCXX_DEBUG
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define ALL(v) v.begin(), v.end()
typedef long long ll;

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; }

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

int main(){
  
  int n;
  cin>>n;
  
  int a,b;
  string x,y;
  while(n--){
    cin>>x>>y;
    a=x.size();
    b=y.size();
    int vec[a+1][b+1];
    rep(i,a+2) vec[i][0]=0;
    rep(i,b+2) vec[0][i]=0;
    for(int i=1;i<a+1;i++){
      for(int j=1;j<b+1;j++){
        if(x[i-1]==y[j-1]) vec[i][j]=vec[i-1][j-1]+1;
        else vec[i][j]=max(vec[i][j-1],vec[i-1][j]);
      }
    }
    cout<<vec[a][b]<<endl;
  }
      
  return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<vector>
#include<string>

using namespace std;

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);

	int q;
	string X,Y;
	//unsigned char 
	int dp[99][99];
	
	dp[0][0] = 0; dp[0][1] = 0; dp[1][0] = 0;

	cin >> q;
	for(int k=0; k < q; k++){
		cin >> X >> Y;
		int i,j;
		for(i=0;i<X.size();i++){
			for(j=0;j<Y.size();j++){
				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[i][j] << "\n";
	}
	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 = 0; i <= m; i++) {
    c[i][0] = 0;
  }
  for (int j = 1; i < n; i++) {
    c[0][j] = 0;
  }

  for (int i = 1; i <= m; i++) {
    for (int j = 1; j <= n; j++) {
      if (X[i] == Y[i]) {
        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;
}