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<cstdio>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<queue>
#include<map>
#include<stack>
#include<set>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int MAX_N=100000;
const int INF = 0x3f3f3f3f;

int dp[1010][1010];
int main(){
	ios::sync_with_stdio(false);
	int t;
	string a,b;
	cin>>t;
	while(t--){
		memset(dp,0,sizeof(dp));
		cin>>a>>b;
		int lena=a.length();
		int lenb=b.length();
		for(int i=1;i<=lena;i++){
			for(int j=1;j<=lenb;j++){
				if(a[i-1]==b[j-1]){
					dp[i][j]=dp[i-1][j-1]+1;
				}
				else{
					dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
				}
			}
		}
		cout<<dp[lena][lenb]<<endl;
	}


	return 0;
}

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

class TLcsSolver
{
    typedef std::vector<std::vector<int> > TTable;
    TTable FTable;
    std::string FArray1;
    std::string FArray2;

    int Count(int i, int j)
    {
        if(i == 0 || j == 0) return 0;
        if(FArray1[i-1] == FArray2[j-1]){
            return FTable[i-1][j-1] + 1;
        }
        return std::max(FTable[i-1][j], FTable[i][j-1]);
    }
    void Solve()
    {
        for(std::size_t i = 1; i < FTable.size(); ++i){
            for(std::size_t j = 1; j < FTable[i].size(); ++j){
                FTable[i][j] = Count(i, j);
            }
        }
    }
public:
    TLcsSolver(const std::string& a, const std::string& b)
     : FArray1(a), FArray2(b)
     , FTable(a.size()+1, std::vector<int>(b.size()+1, 0))
    {
        Solve();
        // Print();
    }
    int Answer()const
    {
        return FTable[FArray1.size()][FArray2.size()];
    }
    void Print()const
    {
        for(std::size_t i = 0; i < FTable.size(); ++i){
            for(std::size_t j = 0; j < FTable[i].size(); ++j){
                std::cout << FTable[i][j] << '\t';
            }
            std::cout << '\n';
        }
    } 
};

int main()
{
    int n;
    std::cin >> n;
    char a[1000];
    char b[1000];
    for(int i = 0; i < n; ++i){
        std::gets(a);
        std::gets(b);
        std::printf("%d", TLcsSolver(a, b).Answer());
    }
    return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <stack>
#include <string>
#include <queue>
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include <vector>
#include <list>
#include <string.h>
#define _USE_MATH_DEFINES
#include <math.h>
#include <map>
#define INFTY (1<<30)
#define MAX 100000000

using namespace std;

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

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

	return 0;
}

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

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

#define N 1000

int lcs(string X, string Y) {
  int m = X.size();
  int n = Y.size();
  int c[m + 1][n + 1];
  int maxlen = 0;
  X = ' ' + X;
  Y = ' ' + Y;
  FOR(i, 1, m + 1) c[i][0] = 0;
  FOR(j, 1, n + 1) c[0][j] = 0;

  FOR(i, 1, m + 1) {
    FOR(j, 1, n + 1) {
      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]);
      }
      maxlen = max(maxlen, c[i][j]);
    }
  }

  return maxlen;
}

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

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

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

    string x, y;
    while (n--)
    {
        cin >> x >> y;
        int c[x.size() + 1][y.size() + 1];
        for (int i = 0; i <= x.size(); i++)
            c[i][0] = 0;
        for (int i = 0; i <= y.size(); i++)
            c[0][i] = 0;

        for (int i = 1; i <= x.size(); i++)
        {
            for (int j = 1; j <= y.size(); j++)
            {
                if (x[i - 1] == y[j - 1])
                    c[i][j] = c[i - 1][j - 1] + 1;
                else
                    c[i][j] = max(c[i - 1][j], c[i][j - 1]);
            }
        }
        cout << c[x.size()][y.size()] << endl;
    }
}

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

using namespace std;

int solve(string x, string y, int xlen, int ylen) {
    vector<vector<int>> dp(xlen + 1, vector<int>(ylen + 1, 0));
    for (int i = 1; i < xlen + 1; i++) {
        for (int j = 1; j < ylen + 1; j++) {
            if (x[i - 1] == y[j - 1]) {
                dp[i][j] = dp[i - 1][j - 1] + 1;
            }
            else {
                dp[i][j] = max(dp[i][j - 1], dp[i - 1][j]);
            }
        }
    }
    return dp[xlen][ylen];
}

int main() {

    int n;
    string x, y;

    cin >> n;
    
    for (int i = 0; i < n; i++) {
        cin >> x >> y;

        cout << solve(x, y, x.length(), y.length()) << endl;

    }
    
    return 0;
}