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 <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef pair<ll,ll> pl;
typedef vector<pl> vp;
#define fore(i,a,b) for(ll i=(a);i<=(b);++i)
#define rep(i,n) fore(i,0,(n)-1)
#define rfore(i,a,b) for(ll i=(b);i>=(a);--i)
#define rrep(i,n) rfore(i,0,(n)-1)
#define all(x) (x).begin(),(x).end()
const ll INF=1001001001;
const ll LINF=1001001001001001001;
const ll D4[]={0,1,0,-1,0};
const ll D8[]={0,1,1,0,-1,-1,1,-1,0};
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;}

void solve(){
    ll n;cin>>n;
    while(n--){
        string s,t;cin>>s>>t;
        ll l1=s.size(),l2=t.size();
        vvl dp(l1+1,vl(l2+1));
        rep(i,l1)rep(j,l2){
            dp[i+1][j+1]=max(dp[i][j+1],dp[i+1][j]);
            if(s[i]==t[j])dp[i+1][j+1]=dp[i][j]+1;
        }
        cout<<dp[l1][l2]<<endl;
    }
}

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

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

void fnInput(vector<string>& rvsStrX, vector<string>& rvsStrY)
{
  int nMaxSiz;
  cin >> nMaxSiz;
  rvsStrX.resize(nMaxSiz);
  rvsStrY.resize(nMaxSiz);

  for (int i = 0; i < nMaxSiz; ++i)
  {
    cin >> rvsStrX[i] >> rvsStrY[i];
    rvsStrX[i] = ' ' + rvsStrX[i];
    rvsStrY[i] = ' ' + rvsStrY[i];
  }
}

int fnLngCmnSubseq(const vector<string>& cnrvsStrX, const vector<string>& cnrvsStrY)
{
  vector<vector<int>> vvnLcsDP;
  for (int i = 0; i < cnrvsStrX.size(); ++i)
  {
    const int nMAXNX = cnrvsStrX[i].size();
    const int nMAXNY = cnrvsStrY[i].size();

    vvnLcsDP.clear();
    vvnLcsDP.resize(nMAXNX, vector<int>(nMAXNY, 0));

    for (int nx = 1; nx < nMAXNX; ++nx)
      for (int ny = 1; ny < nMAXNY; ++ny)
        if (cnrvsStrX[i][nx] == cnrvsStrY[i][ny])
          vvnLcsDP[nx][ny] = vvnLcsDP[nx - 1][ny - 1] + 1;
        else
          vvnLcsDP[nx][ny] = max(vvnLcsDP[nx - 1][ny], vvnLcsDP[nx][ny - 1]);

    cout << vvnLcsDP[nMAXNX - 1][nMAXNY - 1] << endl;
  }
}

int main()
{
  cin.tie(0);
  ios::sync_with_stdio(false);
  vector<string> vsStrX, vsStrY;

  fnInput(vsStrX, vsStrY);
  fnLngCmnSubseq(vsStrX, vsStrY);
  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;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(void){
    int n;
    string str1,str2;
    cin >> n;
    for(int i=0;i<n;i++){
        cin >> str1 >> str2;
        cout << lcs(str1,str2) << endl;
    }
    return 0;
}

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

using namespace std;

#define REP(var, count) for(int var=0; var<count; var++)

int dp[1010][1010];

int main(void) {
	int Q;
	cin >> Q;
	
	REP(data, Q) {
		
		string xstr, ystr;
		cin >> xstr;
		cin >> ystr;
		
		for(int x=0; x<xstr.size()+1; x++) {
			dp[x][0] = 0;
			
			for(int y=1; y<ystr.size()+1; y++) {
				if (x==0) { dp[0][y] = 0; continue; }
				
				if ( xstr[x-1] == ystr[y-1] ) {
					dp[x][y] = dp[x-1][y-1] + 1;
				} else {
					dp[x][y] = max(dp[x-1][y], dp[x][y-1]);
				}
				
			}
		}
		
		cout << dp[xstr.size()][ystr.size()] << endl;
	}

}

C++: #include<iostream>
#include<iomanip>
#include<cmath>
#include<string>
#include<vector>
#include<list>
#include<algorithm>
#include<map>
#include<set>
#include<queue>
#include<stack>
using namespace std;
typedef long long ll;
#define fi first
#define se second
#define mp make_pair
#define rep(i, n) for(int i=0;i<n;++i)
#define rrep(i, n) for(int i=n;i>=0;--i)
const int inf=1e9+7;
const ll mod=1e9+7;
const ll big=1e18;
const double PI=2*asin(1);

int DP[1005][1005];

int main() {
    int N;
    cin>>N;
    string S, T;
    int ans[N];
    for(int i=0;i<N;++i){
        cin>>S>>T;
        for(int j=0;j<S.size();++j){
            for(int k=0;k<T.size();++k){
                DP[j][k] = 0;
            }
        }
        if(S[0]==T[0]) DP[0][0] = 1;
        for(int j=1;j<S.size();++j){
            if(S[j]==T[0]) DP[j][0] = 1;
            DP[j][0] = max(DP[j-1][0], DP[j][0]);
        }
        for(int j=1;j<T.size();++j){
            if(S[0]==T[j]) DP[0][j] = 1;
            DP[0][j] = max(DP[0][j-1], DP[0][j]);
        }
        for(int j=1;j<S.size();++j){
            for(int k=1;k<T.size();++k){
                if(S[j]==T[k]) DP[j][k] = DP[j-1][k-1] + 1;
                else DP[j][k] = max(DP[j-1][k], DP[j][k-1]);
            }
        }
        ans[i] = DP[S.size()-1][T.size()-1];
    }
    for(int i=0;i<N;++i){
        cout<<ans[i]<<endl;
    }
}

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

using namespace std;

int lcs(string a, string b)
{
	vector<vector<int> > dp(1001, vector<int>(1001));
	for (int i = 0; i < a.size(); ++i)
	{
		for (int j = 0; j < b.size(); ++j)
		{
			if (a[i] == b[j])
			{
				dp[i + 1][j + 1] = dp[i][j] + 1;
			}
			else
			{
				dp[i + 1][j + 1] = max(dp[i + 1][j], dp[i][j + 1]);
			}
		}
	}
	return(dp[a.size()][b.size()]);
}

void solve()
{
	int q;
	cin >> q;
	for (int i = 0; i < q; ++i)
	{
		string a, b;
		cin >> a >> b;
		cout << lcs(a, b) << endl;
	}
}

int main()
{
	solve();
	return(0);
}