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>
#include<iostream>
#include<cstdio>
#include<vector>
#include<string>
#include<algorithm>
using namespace std;
#define rep(i,x) for(int i = 0; i < x; i++)
#define pb(x) push_back(x)
#define mp(x,y) make_pair(x,y)
typedef long long ll;
typedef pair<int,int> P;
typedef vector<int> ivec;
const ll N = 1e9+7;

int main(){
    int q; cin >> q;
    string x[q],y[q];
    rep(i,q){
        cin >> x[i] >> y[i];
    }
    int ans[q];
    rep(i,q){
        int dp[1010][1010] = {};
        int xlen = x[i].size();
        int ylen = y[i].size();
        // cout << x[i] << ' ' << xlen << ' ' << y[i] << ' ' << ylen << endl;
        dp[0][0] = 0;
        rep(j,xlen+1){
            if(!j)continue;
            rep(k,ylen+1){
                if(!k)continue;
                if(x[i][j-1] == y[i][k-1]) {
                    dp[j][k] = dp[j-1][k-1] + 1;
                    // cout << i  << ' ' << j  << ' ' << k << ' ' <<  dp[j][k] << endl;
                }
                else{
                    dp[j][k] = max(dp[j-1][k],max(dp[j][k-1],dp[j-1][k-1]));
                }
            }
        }
        ans[i] = dp[xlen][ylen];
    }

    rep(i,q) cout << ans[i] << endl;
    return 0;
}

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

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

static const int N = 10000;

int lcs(string X, string Y);

int main(void){
	string s1, s2;
	int n; cin >> n;
	int i;
	REP(i, n) {
		cin >> s1 >> s2;
		cout << lcs(s1, s2) << endl;
	}
	return 0;
}

// longest common sequence
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;
	int i, j;
	FOR(i, 1, m + 1) FOR(j, 1, n + 1) {
		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;
}

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

using namespace std;

#define N 1000

int LCS(string x, string y){
  int apx[N+1][N+1];
  int a=x.size();
  int k=y.size();
  int max_l =0;

  x=' '+x;
  y=' '+y;

  for(int i=0;i<=a;i++) apx[i][0] =0;
  for(int j=0;j<=k;j++) apx[0][j] =0;

  for(int i=1;i<=a;i++){
    for(int j=1;j<=k;j++){
      if(x[i] == y[j])  apx[i][j] = apx[i-1][j-1] +1;
      else apx[i][j] = max(apx[i-1][j],apx[i][j-1]);
      max_l=max(max_l,apx[i][j]);
    }
  }
  return max_l;
}


int main(){
  int q;
  string x,y;

  cin >> q;

  for(int i=0;i<q;i++){
    cin >> x >> y;
    cout << LCS(x,y) << endl;
  }
  return 0;


}

C++: #include <iostream>
#include <set>
#include <math.h>
#include <list>
#include <vector>
#include <map>
#include <algorithm>
using namespace std;
#define rep(i, n) for (int i = 0; i < n; i++)
#define MAX_N 1005
#define MAX_M 100

long long A[MAX_N];
long long B[MAX_N];
int MOD = 1000000000 + 7;
string S;

int dp[MAX_N][MAX_N];
int lcs(string S, string T)
{
    rep(i, S.length())
    {
        rep(j, T.length())
        {
            if (S[i] == T[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[S.length()][T.length()];
}

int main()
{
    rep(i, MAX_N)
    {
        dp[i][0] = 0;
        dp[0][i] = 0;
    }
    int Q;
    cin >> Q;
    string S, T;
    rep(i, Q)
    {
        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 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() {
  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 <algorithm>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <cmath>
#include <cstring>

#define LP(i,n) for(int i=0;i<n;i++)
#define Mset(x,v) memset(x,v,sizeof(x))

using namespace std;
using LL=long long;

int main(){
    int n,x,y,maxl;
    string X,Y;
    cin>>n;
    LP(i,n){
        int c[1001][1001];
        cin>>X>>Y;
        x=X.size();
        y=Y.size();
        X=' '+X;
        Y=' '+Y;
        maxl=0;
        for(int j=0;j<=x;j++) c[j][0]=0;
        for(int j=1;j<=y;j++) c[0][j]=0;
        for(int j=1;j<=x; j++){
            for(int k=1;k<=y;k++){
                if(X[j]==Y[k]){
                    c[j][k]=c[j-1][k-1]+1;
                }
                else{
                    c[j][k]=max(c[j-1][k],c[j][k-1]);
                }
                maxl=max(maxl,c[j][k]);
            }
        }
        cout<<maxl<<endl;
    }
    return 0;
}