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 <algorithm>
#include <cmath>
#include <cstdio>
#include <vector>

int constexpr MAX = 1000;
char ls[MAX];
char rs[MAX];
int table[MAX + 1][MAX + 1];


void calc_lcs() {
    scanf("%s", ls);
    scanf("%s", rs);
    int l_len = int(strlen(ls));
    int r_len = int(strlen(rs));
    for (int i = 0; i < l_len; i++) {
        table[i][0] = 0;
    }
    for (int i = 0; i < r_len; i++) {
        table[0][i] = 0;
    }

    for (int l_i = 1; l_i < l_len + 1; l_i++) {
        for (int r_i = 1; r_i < r_len + 1; r_i++) {
            if (ls[l_i - 1] == rs[r_i - 1]) {
                table[l_i][r_i] = table[l_i - 1][r_i - 1] + 1;
            } else {
                table[l_i][r_i] = std::max(table[l_i][r_i - 1], table[l_i - 1][r_i]);
            }
        }
    }
    std::cout << table[l_len][r_len] << std::endl;
}

int main() {
    int N;
    scanf("%d", &N);
    for (int i = 0; i < N; i++) {
        calc_lcs();
    }
}

C++: #include <iostream>
#include <string>
#include <cstring>
#define repi(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,a) repi(i,0,a)
#define clr(a,v) memset((a),(v),sizeof(a))

int q;
int dp[1000][1000];
std::string s, t;

int rec( int i, int j )
{
  int &ret = dp[i][j];

  if( ~ret )
    return ret;

  if( i == s.size() || j == t.size() )
    return 0;

  ret = 0;

  if( s[i] == t[j] )
    ret = std::max( ret, rec( i+1, j+1 )+1 );

  ret = std::max( ret, std::max( rec( i+1, j ), rec( i, j+1 ) ) );

  return ret;
}

int main()
{
  scanf( "%d", &q );
  while( q-- )
  {
    std::cin >> s >> t;

    clr( dp, -1 );

    std::cout << rec( 0, 0 ) << std::endl;
  }

  return 0;
}

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

int main() {
    int dataSet;
    std::cin >> dataSet;

    for(int count = 0; count < dataSet; count++) {
        std::string x, y;
        std::cin >> x;
        std::cin >> y;

        std::vector< std::vector<int> > dp;
        dp.resize(x.length());
        for(auto itr = dp.begin(); itr < dp.end(); itr++) {
            itr->resize(y.length());
        }

        for(int xIndex = 0; xIndex < x.length(); xIndex++) {
            for(int yIndex = 0; yIndex < y.length(); yIndex++) {
                int top, topleft, left;
                top = 0; topleft = 0; left = 0;
                if(xIndex != 0) {
                    top = dp[xIndex - 1][yIndex];
                }
                if(yIndex != 0){
                    left = dp[xIndex][yIndex - 1];
                }
                if(xIndex != 0 && yIndex != 0) {
                    topleft = dp[xIndex - 1][yIndex - 1];
                }

                if(x[xIndex] == y[yIndex]) {
                    dp[xIndex][yIndex] = topleft + 1;
                } else {
                    dp[xIndex][yIndex] = top < left ? left : top;
                }
            }
        }

        std::cout << dp.back().back() << std::endl;
    }

    return 0;
}

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

using std::cin;
using std::cout;
using std::cerr;
using std::endl;

// 最長共通部分列 ... len(s) == m, len(t) == n とすると, O(mn)
int lcs(std::string s, std::string t) {
  std::vector<std::vector<int> > dp(s.size() + 1, std::vector<int>(t.size() + 1, 0));

  for (int i = 1; i <= s.size(); ++i) {
    for (int j = 1; j <= t.size(); ++j) {
      if (s[i - 1] == t[j - 1]) {
        dp[i][j] = dp[i - 1][j - 1] + 1;
      }
      else if (dp[i - 1][j] >= dp[j][i - 1]) {
        dp[i][j] = dp[i - 1][j];
      }
      else {
        dp[i][j] = dp[i][j - 1];
      }
    }
  }

  return dp[s.size()][t.size()];
}

int main() {
  int q;
  std::string s, t;
  cin >> q;
  while (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 = 1; i <= m; i++) c[i][0] = 0;
  for ( int j = 1; i <= 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>
using namespace std;

static const int N = 1000;
int dp[N + 1][N + 1];

int lcs(string x, string y)
{
    int m = x.length();
    int n = y.length();
    x = ' ' + x;
    y = ' ' + y;

    dp[0][0] = 0;
    for (int i = 1; i <= m; i++)
        dp[i][0] = 0;
    for (int j = 1; j <= n; j++)
        dp[0][j] = 0;

    int res = 0;
    for (int i = 1; i <= m; i++)
    {
        for (int j = 1; j <= n; 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]);
        }
    }

    return dp[m][n];
}

int main()
{
    int n;
    cin >> n;
    string x1, x2;
    for (int i = 0; i < n; i++)
    {
        cin >> x1 >> x2;
        cout << lcs(x1, x2) << endl;
    }
    return 0;
}