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<string.h>
using namespace std;
int LCS(char *x,char *y);
char x[1001], y[1001];
int lcs[1001][1001];
int main()
{
	int q,i,j;

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

int LCS(char *x, char *y)
{
	int i, j;
	int len_x, len_y;
	len_x = strlen(x);
	len_y = strlen(y);
	
	for (i = 1; i <+ len_x; i++) {
		for (j = 1; j <+ len_y; j++) {
			if (x[i-1] == y[j-1]) {
				lcs[i][j] = lcs[i - 1][j - 1] + 1;
				//printf("lcs[%d][%d]=%d\n", i, j, lcs[i - 1][j - 1] + 1);
			}
			if (x[i] != y[j]) {
				lcs[i][j] = max(lcs[i - 1][j], lcs[i][j - 1]);
				//printf("lcs[%d][%d]=%d\n", i, j, max(lcs[i - 1][j], lcs[i][j - 1]));
			}
		}
	//cout << endl;

	}
	for (i = 0; i < len_x; i++) {
		for (j = 0; j < len_y; j++) {
			//printf("%d ", lcs[i][j]);
		}
		//cout << endl;
	}
	//cout << "len_x=" << len_x << endl << "len_y=" << len_y << endl;
			
	return lcs[i-1][j-1];
}

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

using namespace std;

static const int N = 1000;
static int c[N + 1][N + 1] = {};

static int lcs(string& X, string& Y) {
  const size_t m(X.size());
  const size_t n(Y.size());
  X = ' ' + X;
  Y = ' ' + Y;

  int lcs = 0;
  
  for (size_t i = 1; i <= m; i++) {
    for (size_t 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]);
      }
      lcs = max(lcs, c[i][j]);
    }
  }
  return lcs;
}

int main() {
  int n;
  cin >> n;

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

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

int lcs(string X, string Y) {
  int dp[1000 + 1][1000 + 1];
  int max = 0;
  int m = X.size();
  int n = Y.size();
  X = ' ' + X;
  Y = ' ' + Y;
  for(int i = 1; i <= m; i++)
    dp[i][0] = 0;
  for(int i = 1; i <= n; i++)
    dp[0][i] = 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 if(dp[i - 1][j] >= dp[i][j - 1])
	dp[i][j] = dp[i - 1][j];
      
      else
	dp[i][j] = dp[i][j - 1];
      if(max < dp[i][j])
	max = dp[i][j];
    }
  }
  return max;
}

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

C++: #include<bits/stdc++.h>

using namespace std;

int lcs(string X,string Y){
  //staticにしないと実行時にスタックオーバーフローになる
  static int c[1001][1001];
  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(){
  int q;cin>>q;
  while(q--){
    string a,b;cin>>a>>b;
    cout << lcs(a,b);
  }
  return 0;
}

C++: #include <iostream>

using namespace std;

int lcs(string X, string Y) {
  int memo[1010][1010];
  // 初期化
  for (int i = 0; i < X.size(); i++) {
    memo[i][0] = 0;
  }
  for (int i = 0; i < Y.size(); i++) {
    memo[0][i] = 0;
  }
  int maxl = 0;
  for (int i = 0; i < X.size(); i++) {
    for (int j = 0; j < Y.size(); j++) {
      if (X[i] == Y[j]) {
        memo[i][j] = memo[i-1][j-1] + 1;
      } else {
        memo[i][j] = max(memo[i-1][j], memo[i][j-1]);
      }
      maxl = max(maxl, memo[i][j]);
    }
  }
  return maxl;
}

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

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


using namespace std;int n[1003][1003]={};
int main(){

string A,B;
int N;
cin>>N;
for(int I=0;I<N;I++){
	cin>>A;cin>>B;

	
	int max=0;
	for(int i=0;i<(int)A.size();i++)
		for(int j=0;j<(int)B.size();j++)
			{
				
				if(A[i]==B[j])n[i+1][j+1]=n[i][j]+1;
				else{
					n[i+1][j+1]=n[i+1][j];
				if(n[i][j+1]>n[i+1][j])n[i+1][j+1]=n[i][j+1];
				}
				
		}
		
		
		
		for(int i=A.size()+1;i>=0;i--){int c=0;int y=i;
		for(int j=B.size()+1;j>=0;j--)
		{if(n[y][j]==n[y-1][j-1]+1&&y>0){y--;c++;
		}
	}
		if(max<c)max=c;
		}
		cout<<max<<endl;
}
return 0;
}

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

int main(){
  int n;
  cin >> n;

  vector<int> anss;
  for (int i = 0; i < n; i++)
  {
    string s,t;
    cin >> s >> t;

    int lens = s.size();
    int lent = t.size();
    int dp[lens][lent];
    bool flg = false;
    for (int j = 0; j < lens; j++)
    {
      if(t[0]==s[j]) flg = true;
      if(flg) dp[j][0] = 1;
      else dp[j][0] = 0;
    }
    flg = false;
    for (int j = 0; j < lent; j++)
    {
      if(s[0]==t[j]) flg = true;
      if(flg) dp[0][j] = 1;
      else dp[0][j] = 0;
    }

    for (int j = 1; j < lens; j++)
    {
      for (int k = 1; k < lent; k++)
      {
        if(s[j]==t[k]) dp[j][k] = dp[j-1][k-1]+1;
        else dp[j][k] = max(dp[j-1][k],dp[j][k-1]);
      }      
    }
    anss.push_back(dp[lens-1][lent-1]);
  }
  for(int ans:anss) cout << ans << endl;
}

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

int main() {
  int q; cin >> q;
  string A, B;
  for (int i=0; i<q; i++) {
    cin >> A >> B;
    vector<vector<int>> LCS(A.length()+1, vector<int>(B.length()+1,0));
    int ans=0;
    for (int j=1; j<=A.length(); j++) {
      for (int k=1; k<=B.length(); k++) {
        if(A[j]==B[k]) LCS[j][k]=LCS[j-1][k-1]+1;
        else LCS[j][k]=max(LCS[j-1][k],LCS[j][k-1]);
        ans = max(ans, LCS[j][k]);
      }
    }
    cout << ans << "\n";
  }
}