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>
using namespace std;

int calcLCS(string s, string t) {
    if (s.length() < t.length()) {
        string temp = s;
        s = t;
        t = temp;
    }

    int table[s.length()+1][t.length()+1];
    for (int i=0; i<=s.length(); i++) {
        table[i][0] = 0;
    }
    for (int j=0; j<=t.length(); j++) {
        table[0][j] = 0;
    }

    for (int i=1; i<=s.length(); i++) {
        for (int j=1; j<=t.length(); j++) {
            if (s.at(i-1) == t.at(j-1)) {
                table[i][j] = table[i-1][j-1] + 1;
            } else {
                table[i][j] = max(table[i][j-1], table[i-1][j]);
            }
        }
    }

    return table[s.length()][t.length()];
}

int main() {
    int n;
    cin >> n;
    for (int i=0; i<2*n; i+=2) {
        string x, y;
        cin >> x >> y;

        cout << calcLCS(x, y) << endl;
    }

    return 0;
}

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

int main()
{
    int n;
    cin >> n;
    while(n)
    {
        n--;
        string X,Y;
        int i=0,j=0;
        cin >> X;
        cin >> Y;
        int L[1001][1001];
        for(i=0;i<1001;i++)
            for(j=0;j<1001;j++)
               L[i][j]=0;
        for(i=1;i<=X.size();i++)
            for(j=1;j<=Y.size();j++)
            {
                if(X[i-1]==Y[j-1])
                    L[i][j]=1+L[i-1][j-1];
                else    L[i][j]=max(L[i][j-1],L[i-1][j]);
            }
        cout << L[X.size()][Y.size()] << endl;
    }
    return 0;
}

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

using namespace std;
static const int N = 1000;

int lenCommon(string s1, string s2)
{
	int len = max(int(s1.size()), int(s2.size()));
	vector<vector<int> > dp(N+1, vector<int>(N+1, 0));

	s1 = " " + s1;
	s2 = " " + s2;

	for (int i = 0; i <= len; ++i) dp[i][0] = 0;
	for (int i = 0; i <= len; ++i) dp[0][i] = 0;

	int ret = 0;
	for (int i = 1; i <= len; ++i)
	{
		for (int j = 1; j <= len; ++j)
		{
			if (s1[i] == s2[j])
				dp[i][j] = dp[i - 1][j - 1] + 1;
			else
				dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);

			ret = max(ret, dp[i][j]);
		}
	}
	return ret;
}

int main()
{
	string s1, s2;
	int num; cin >> num;
	for (int i = 0; i < num; ++i)
	{
		cin >> s1 >> s2;
 		int res = lenCommon(s1, s2);
		cout << res << endl;
	}
}

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

using namespace std;

#define max(a, b) a > b ? a : b;

int main() {
  int q;
  int i, j, k;
  string x, y;
  cin >> q;
  for (i = 0; i < q; i++) {
    int maxVal = 0;
    cin >> x;
    cin >> y;
    int lenx = x.size();
    int leny = y.size();
    x = ' ' + x;
    y = ' ' + y;
    int c[lenx + 1][leny + 1];
    for (j = 0; j <= lenx; ++j) {
      c[j][0] = 0;
    }
    for (j = 0; j <= leny; ++j) {
      c[0][j] = 0;
    }
    for (j = 1; j <= lenx; ++j) {
      for (k = 1; k <= leny; ++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]);
        }
        maxVal = max(maxVal, c[j][k]);
      }
    }
    cout << maxVal << '\n';
  }

  return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <algorithm>
#include <string>
#include <cstring>
#include <cctype>
#include <cmath>
#include <stack>
#include <queue>
#include <vector>
#include <set>
#include <map>
#include <list>
#include <stdio.h>
#include <string.h>
#include <cstdlib>
#include <math.h>
#include <bitset>
#include <iterator>
#include <iomanip>
#include <sstream>
#define INF 2000000000
using namespace std;
int dx[4]={1,0,-1,0},dy[4]={0,1,0,-1};
#define sym cout<<"---------"<<endl;
#define ll long long
#define PL pair<long long, long long>
#define P pair<int,int>
#define mk make_pair
#define en endl
#define WHITE 0
#define BLACK 2
#define GRAY 1
#define RE return 0
#define int ll

//  最長共通部分列

int dp[1005][1005];

signed main(){
  int n;
  cin>>n;
  for(int i=0; i<n; i++){
    string s1,s2;
    cin>>s1>>s2;
    s1=" "+s1;
    s2=" "+s2;
    int maxl=0;
    for(int i=0; i<=s1.size()-1; i++) for(int j=0; j<=s2.size(); j++) dp[i][j]=0;
    for(int i=1; i<=s1.size()-1; i++){
      for(int j=1; j<=s2.size(); j++){
        if(s1[i]==s2[j]) dp[i][j]=dp[i-1][j-1]+1;
        else dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
        maxl=max(maxl,dp[i][j]);
      }
    }
    cout<<maxl<<en;
  }
}

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

using namespace std;

int lcs(string x,string y){
  int m=x.size();
  int n=y.size();
  int c[m+1][n+1];
  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]);
    }
  }
  return c[m][n];
}

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