Go: package main

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

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 500001), 500000)
	return scanner
}

func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}

func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}

func main() {
	fp := os.Stdin
	if len(os.Args) > 1 {
		fp, _ = os.Open(os.Args[1])
	}

	scanner := getScanner(fp)
	writer := bufio.NewWriter(os.Stdout)

	n := getNextInt(scanner)
	for i := 0; i < n; i++ {
		x := getNextString(scanner)
		y := getNextString(scanner)

		fmt.Fprintln(writer, lcs(x, y))
	}

	writer.Flush()
}

func lcs(x, y string) int {
	lx := len(x)
	ly := len(y)
	dp := make([][]int, lx+1)
	for i := 0; i <= lx; i++ {
		dp[i] = make([]int, ly+1)
	}
	for i := 0; i < lx; i++ {
		for ii := 0; ii < ly; ii++ {
			if x[i] == y[ii] {
				dp[i+1][ii+1] = dp[i][ii] + 1
				continue
			}
			dp[i+1][ii+1] = dp[i][ii+1]
			if dp[i+1][ii] > dp[i+1][ii+1] {
				dp[i+1][ii+1] = dp[i+1][ii]
			}
		}
	}
	return dp[lx][ly]
}

C++: #include<bits/stdc++.h>
using namespace std;
int dp[2][1010];
int main(){
  int q;
  cin>>q;
  for(int cn=0;cn<q;cn++){
    string x,y;
    cin>>x>>y;
    memset(dp,0,sizeof(dp));
    for(int i=0;i<x.size();i++){
      int nw=i%2;
      int nt=!nw;
      for(int k=0;k<1010;k++)dp[nt][k]=0;
      for(int j=0;j<y.size();j++){
	if(j)dp[nw][j]=max(dp[nw][j],dp[nw][j-1]);
	if(x[i]==y[j])dp[nt][j+1]=max(dp[nt][j+1],dp[nw][j]+1);
	dp[nt][j]=max(dp[nt][j],dp[nw][j]);
      }
    }
    int ans=0;
    for(int i=0;i<1010;i++)ans=max(ans,dp[x.size()%2][i]);
    cout<<ans<<endl;
  }
  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define REP(i,n) for(int i=0; i<(n); i++)
#define REP2(i,x,n) for(int i=x; i<(n); i++)
#define PRINT(x) cout<<(x)<<endl
#define INF 1000000000000 // 10^12
#define MOD 1000000007 // 10^9+7
#define PB push_back
#define MP make_pair

const int MAX_X = 1000, MAX_Y = 1000;

int q;
string X, Y;

int dp[MAX_X + 1][MAX_Y + 1];

int main() {
    cin >> q;
    REP(_, q) {
        cin >> X >> Y;
        REP(i, X.size() + 1) {
            REP(j, Y.size() + 1) dp[i][j] = 0;
        }
        REP(i, X.size()) {
            REP(j, Y.size()) {
                dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i][j]);
                dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i][j + 1]);
                dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i + 1][j]);
                if (X[i] == Y[j]) dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i][j] + 1);
            }
        }
        int Z_size = dp[X.size()][Y.size()];
        PRINT(Z_size);
    }
    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();
  
  for (int i = 0; i < m; i++) {
    for (int j = 0; j < n; j++) {
      if (X[i] == Y[j]) 
        if (i == 0 || j == 0) 
          c[i][j] = 1;
        else 
          c[i][j] = c[i - 1][j - 1] + 1;
      else
        if (i != 0 && j != 0) 
          c[i][j] = max(c[i][j - 1], c[i - 1][j]);
        else
          c[i][j] = 0;
    }
  }
  return c[m - 1][n - 1];
}

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 <bits/stdc++.h>

using namespace std;
using ll =long long;
typedef pair<int,int> P;
#define SORT(a) sort((a).begin(),(a).end())
#define rSORT(a) reverse((a).begin(),(a).end())
#define For(i, a, b)    for(int i = (a) ; i < (b) ; ++i)
#define rep(i, n)       For(i, 0, n)
#define debug(x)  cerr << #x << " = " << (x) << endl;
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
//Write From this Line

int main()
{
	int q;
	cin >> q;
	while(q--){
		string a, b;
		cin >> a >> b;
		int dp[1010][1010];
		dp[0][0] = 0;
		rep(i,a.size()){
			rep(j,b.size()){
				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]);
				}
			}
		}
		cout << dp[a.size()][b.size()] << endl;
	}
}

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

using namespace std;

const int MAX = 1000;
int ary[MAX][MAX];

int getVal(int n, int m) {

	if (m >= 0 && n >= 0 && m < MAX && n < MAX) {
		return ary[n][m];
	}
	else {
		return 0;
	}
}

int LCS(string s1, string s2) {

	int m, n;
	m = s1.length();
	n = s2.length();
	const char* c1 = s1.c_str();
	const char* c2 = s2.c_str();

	for (int i = 0;i < n;i++) {
		for (int k = 0;k < m;k++) {

			if (c1[k] != c2[i]) {
				ary[i][k] = max(getVal(i - 1, k), getVal(i, k - 1));
			}
			else if (c1[k] == c2[i]) {
				ary[i][k] = getVal(i - 1, k- 1) + 1;
			}
		}
	}

	return ary[n - 1][m - 1];
}


int main() {


	int num;
	cin >> num;

	string str1, str2;

	for (int i = 0;i < num;i++) {
		cin >> str1 >> str2;

		cout << LCS(str1, str2) << 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;//??¨X[0]????????\?????????
	Y=' '+Y;//??¨Y[0]????????\?????????
	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++: #include <iostream>
#include <string>
#include <vector>


constexpr int MAXLENGTH = 1000;
int C[MAXLENGTH + 1][MAXLENGTH + 1];
int lcs(std::string lhs, std::string rhs) {
    int lnum = lhs.length();
    int rnum = rhs.length();
    for (int i = 0; i <= lnum; i++) {
        C[i][0] = 0;
    }
    for (int i = 0; i <= rnum; i++) {
        C[0][i] = 0;
    }
    for (int il = 1; il <= lnum; il++) {
        for (int ir = 1; ir <= rnum; ir++) {
            if (lhs[il-1] == rhs[ir-1]) {
                C[il][ir] = C[il - 1][ir - 1] + 1;
            }else if(C[il - 1][ir] >= C[il][ir - 1]) {
                C[il][ir] = C[il-1][ir];
            }else{
                C[il][ir] = C[il][ir - 1];
            }
        }
    }
    return C[lnum][rnum];
}

int main() {
    int n;
    std::cin >> n;
    for (int i = 0; i < n; i++) {
        std::string l, r;
        std::cin >> l;
        std::cin >> r;
        std::cout << lcs(l, r) << std::endl;
    }
}

C++: #include <iostream>
#include <vector>
#include <string>
#include <cmath>
#include <set>
#include <algorithm>
#include <array>
#include <complex>
#include <utility>
#include <map>
#include <inttypes.h>

int LCS(std::string s,std::string t){
    int n,m,c[1001][1001]={0};
    n=s.size();
    m=t.size();
    int maxlen=0;
    for(int i=1;i<=n;i++){
        c[i][0]=0; 
    }
    for(int i=1;i<=m;i++){
        c[0][i]=0;
    }
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            if(s[i]==t[j]){
                c[i][j]=c[i-1][j-1]+1;
            }else{
                c[i][j]=std::max(c[i-1][j],c[i][j-1]);
            }
            maxlen=std::max(c[i][j],maxlen);
        }
    }
    return maxlen;
}
int main(){
	int N;
    
    std::cin >> N;
    std::string s1,s2;
    for(int i=0;i<N;i++){
        std::cin >> s1 >> s2;
        std::cout << LCS(s1,s2) <<std::endl;
    }
        
    
    return 0;
}