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 <cstdio>
#include <cstdlib>
#include <cassert>
#include <string>
#include <cstring>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>

using namespace std;

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

// debug
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;

// ---------------------
#define INF 922337203685477580
typedef long long ll;

int dp[1000][1000];

int main() {
  int q;
  cin >> q;
  REP(loop, q) {
    char S[1000], T[1000];
    cin >> S >> T;

    dp[0][0] = 0;
    for (int i = 1; i <= strlen(S); i++) {
      for (int j = 1; j <= strlen(T); j++) {
        if (S[i] == T[j]) {
          dp[i][j] = dp[i - 1][j - 1] + 1;
        } else {
          dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
        }
      }
    }
    cout << dp[strlen(S)][strlen(T)] << endl;
  }

  return 0;
}

C++: #include <stdio.h>
#include <string.h>

#define N 10000

int lcs(char *x,char *y){
	int c[N+1][N+1];
	int m = strlen(x);
	int n = strlen(y);
	int maxl = 0;
	x = strcat(" ",x);
	y = strcat(" ",y);
	int i,j;
	for(i=1;i<=m;i++){
		c[i][0]=0;
	}
	for(j=0;j<=n;j++){
		c[0][j]=0;
	}

	for(i = 1;i<=m;i++){
		for(j=1;j<=n;j++){
			if(x[i]==y[j]){
				c[i][j] = c[i-1][j-1] +1;
			}
			else{
				if(c[i-1][j] > c[i][j-1]) c[i][j] = c[i-1][j];
				else c[i][j] = c[i][j-1];
			}
			if(maxl>c[i][j])maxl = maxl;
			else maxl = c[i][j];
		}
	}
	return maxl;
}

int main(){
	char s1[1000];
	char s2[1000];
	int n;
	scanf("%d",&n);
	int i;
	for(i=0;i<n;i++){
		scanf("%s%s",s1,s2);
		printf("%d\n",lcs(s1,s2));
	}
	return 0;
}

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

using namespace std;

int main(){
  int q;cin >>q;
  for(int i=0;i<q;i++){
    string x,y;cin >> x >> y;
    int lx=x.length();int ly=y.length();
    //cout << lx << ly;
    vector< vector<int> > dp(ly,vector<int>(lx,0));
    int f=0;
    for(int j=0;j<ly;j++){
      if(x[0]==y[j]){f=1;}
      dp[j][0]=f;
    }
    f=0;
    for(int j=0;j<lx;j++){
      if(y[0]==x[j]){f=1;}
      dp[0][j]=f;
    }
    for(int j=0;j<ly;j++){
      for(int k=0;k<lx;k++){
        if(j!=0 and k!=0){
          int l=0;
          if(x[k]==y[j]){l=1;}
          //{}でmaxと同じように使える
          dp[j][k]=max({dp[j-1][k],dp[j][k-1],dp[j-1][k-1]+l});
        }
      }
    }
    cout << dp[ly-1][lx-1] << endl;
  }
}

C++: #define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
using namespace std;
#define len(n) (int)n.length()
#define pb push_back
#define ll long long
#define make_pair mkp
#define REP(i, n) for(int i = 0;i < n;i++)
#define REPR(i, n) for(int i = n;i >= 0;i--)
#define FOR(i, m, n) for(int i = m;i < n;i++)
#define ALL(v) (v).begin(), (v).end()
#ifdef DBGPRT
#define dbg(n) cerr << "//" << #n << ":" << n <<endl
#else
#define dbg(n) ;
#endif
typedef pair<ll, ll> LLARR;
#define INF 999999999
const double PI = 3.1415926535897932384626433832795;

int lcs(string s1, string s2)
{
	int m = len(s1);
	int n = len(s2);
	s1 = ' '+s1;
	s2 = ' '+s2;
	int (*mat)[1001];
	mat = new int[1001][1001];
	REP(i, m)
	{
		mat[i][0] = 0;
	}
	REP(i, n)
	{
		mat[0][i] = 0;
	}
	int maxx = 0;
	FOR(i, 1, m+1)
	{
		FOR(j, 1, n+1)
		{
			if (s1[i] == s2[j])
				mat[i][j] = mat[i-1][j-1] + 1;
			else
				mat[i][j] = max(mat[i][j-1], mat[i-1][j]);
			maxx = max(maxx, mat[i][j]);
		}
	}
	delete[] mat;
	return maxx;
}
int main()
{
	ios::sync_with_stdio(false);

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

C++: #include <iostream>
#include <string>
#define MAX 100001
#define SENTINEL 2000000000
using namespace std;

int solved[MAX];
int d[1001][1001];

void lcs(string a, string b)
{
    int m = a.size();
    int n = b.size();
    a = ' ' + a;
    b = ' ' + b;
    for (int i = 1; i <= m; i++)
    {
        d[i][0] = 0;
    }
    for (int i = 1; i <= n; i++)
    {
        d[0][i] = 0;
    }

    int max_lcs = 0;

    for (int i = 1; i <= m; i++)
    {
        for (int j = 1; j <= n; j++)
        {
            if (a[i] == b[j])
            {
                d[i][j] = d[i - 1][j - 1] + 1;
            }
            else
            {
                d[i][j] = max(d[i - 1][j], d[i][j - 1]);
            }
            max_lcs = max(max_lcs, d[i][j]);
        }
    }
    cout << max_lcs << endl;
}

int main()
{
    int q;
    cin >> q;
    for (int i = 0; i < q; i++)
    {
        string a, b;
        cin >> a >> b;
        lcs(a, b);
    }
    return 0;
}

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

#define MAX 1000

int lcs(string X, string Y) {
    int c[MAX+1][MAX+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 i = 1; i <= n; i++) {
        c[0][i] = 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(c[i][j], maxl);
        }
    }
    return maxl;
}

int main() {
    int n;
    string X, Y; 
    cin >> n;
    for(int i = 0; i < n; i++) {
        cin >> X >> Y;
        cout << lcs(X, Y) << endl;
    }
    return 0;
}