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++: #if 0
PDFに記載されている方針がわかりやすかったので、比較的簡単に解くことができた。
#endif

#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;

int Q;
int L[1000+10][1000+10];

int main() {
  cin >> Q;
  string X, Y;
  for (int i = 0; i < Q; i++) {
    for (int j = 0; j < 1000+10; j++) {
      L[0][j] = 0; L[j][0] = 0;
    }
    cin >> X >> Y;
    for (int x = 1; x <= X.length(); x++) {
      for (int y = 1; y <= Y.length(); y++) {
        if (X[x-1] == Y[y-1])
          L[x][y] = L[x-1][y-1] + 1;
        else
          L[x][y] = max(L[x-1][y], L[x][y-1]);
      }
    }
    cout << L[X.length()][Y.length()] << endl;
  }
}

C++: #include<bits/stdc++.h>
using namespace std;

#define rep(i,n) for(int i = 0; i < n; i++)
#define Rep(i,n) for(int i = 1; i <= n; i++)
#define sz(x) int(x.size())
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define YesorNo(a) printf(a ? "Yes\n" : "No\n")
#define endl '\n'
#define fi first
#define se second
using ll = long long;
using P = pair<int,int>;
using Pl = pair<ll,ll>;
template<class T> using V = vector<T>;
const int dx[] = {0,1,0,-1,1,1,-1,-1};
const int dy[] = {1,0,-1,0,1,-1,-1,1};
const int inf = (1<<30)-1;
const ll infll = (1LL<<62)-1;
ll ceil(const ll &a, const ll &b){return ((a)+(b)-1)/b;}
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; }


int lcs(string s, string t) { // 最長共通部分列長
  int n = s.size();
  int m = t.size();
  vector<vector<int>> dp(n+1,vector<int>(m+1));
  for(int i = 0; i < n; i++) {
    for(int j = 0; j < m; j++) {
      if(s[i] == t[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]);
      dp[i+1][j+1] = max(dp[i+1][j+1], dp[i][j+1]);
    }
  }
  return dp[n][m];
}


int main(){
    int n;
    cin >> n;
    rep(i,n) {
        string s, t;
        cin >> s >> t;
        int ans = lcs(s,t);
        cout << ans << endl;
    }
}

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

using namespace std;

int dp[1010][1010];

int main() {
    int q;  cin >> q;
    int *ans = new int[q];
    string s, t;
    int ls, lt, i, j;
    for (int k = 0; k < q; k++) {
        cin >> s >> t;
        ls = s.size(), lt = t.size();

        for (i = 0; i <= ls; i++) {
            for (j = 0; j <= lt; j++)
                dp[i][j] = 0;
        }

        for (i = 0; i < ls; i++) {
            for (j = 0; j <= lt; j++) {
                if (s[i] == t[j])
                    dp[i+1][j+1] = max(dp[i][j]+1, max(dp[i+1][j], dp[i][j+1]));
                else
                    dp[i+1][j+1] = max(dp[i+1][j], dp[i][j+1]);
            }
        }   
        ans[k] = dp[ls][lt];
    }
    for (int k = 0; k < q; k++)
        cout << ans[k] << endl;
    return 0;
}

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

using namespace std;

#define 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 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(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 <vector>
# include <string>
# include <set>
# include <map>
# include <cmath>
# include <iomanip>
# include <functional>
# include <utility>
# include <stack>
# include <queue>
# include <list>
constexpr int MOD = 1000000007;
constexpr int INF = 2000000000;
using namespace std;

int lcs(string x, string y) {
	int c[1200][1200];
	int m = x.size();
	int n = y.size();
	x = ' ' + x;
	y = ' ' + y;
	for (int i = 1; i <= m; i++) c[i][0] = 0;
	for (int j = 1; j <= n; j++) c[0][j] = 0;
	c[0][0] = 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]);
			}
		}
	}
	return c[m][n];
}

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

C++: #include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; ++i)
#define ALL(v) v.begin(), v.end()
typedef long long ll;
typedef pair<int, int> P;
const int INF = 100000000;


int main()
{
	int N;
	cin >> N;
	rep(ii,N)
	{
	string s,t;
	cin >> s >> t;
	int n=s.size(),m=t.size();
	vector<vector<int>> dp(n+1,vector<int>(m+1,0));
	for(int i=0;i<n;i++)
	{
		for(int j=0;j<m;j++)
		{
			if(s[i]==t[j])
			{
				dp[i+1][j+1] = dp[i][j]+1;

			}
			else
			{
				dp[i+1][j+1] = max(dp[i][j+1],dp[i+1][j]);
			}
		}
	}
	cout<<dp[n][m]<<endl;
	}
	return 0;
}