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 ll = long long;
using namespace std;
#define rep(i,n) for(int i=0, i##_len=(int)(n); i<i##_len; i++)
#define reps(i,n) for(int i=1 , i##_len=(int)(n);i<=i##_len;i++)
#define rrep(i,n) for(int i=((int)(n)-1);i>=0;i--)
#define rreps(i,n) for(int i=((int)(n));i>0;i--)
#define all(x) (x).begin(), (x).end()
#define F first
#define S second
#define mp make_pair
#define pb push_back
#define solve(a) ((a)?"Yes":"No")
typedef vector<long long> V;
typedef vector<V> VV;
typedef pair<long long , long long> P;
typedef vector<P> VP;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1;} return 0;}
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1;} return 0;}
const long long INFLL = 1LL<<62;
const int INF = 1<<30;
const double PI=acos(-1);
int main(){
    int n;
    cin >>n;
    int a=0,b=0;
    string x,y;
    vector<vector<int>>dp(1010,vector<int>(1010,0));
    rep(_,n){
        rep(i,a+1){
            rep(j,b+1){
                dp[i][j]=0;
            }

        }
        cin>>x>>y;
        a=x.size();
        b=y.size();
       
        rep(i,a){
            rep(j,b){
                
                    chmax(dp[i+1][j+1],dp[i][j+1]);
                
                if(j!=0){
                    chmax(dp[i+1][j+1],dp[i+1][j]);
                }
                if(x[i]==y[j]){
                    chmax(dp[i+1][j+1],dp[i][j]+1);
                }
            }
        }
        cout<<dp[a][b]<<endl;
    }
    
}

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

const int MAX_N=1e3+5;

string s1,s2;

int dp[MAX_N][MAX_N];


int lcs(int i,int j){
	if(i==s1.size() || j==s2.size())return 0;
	if(dp[i][j]!=-1)return dp[i][j];
	if(s1[i]==s2[j])return dp[i][j]=lcs(i+1,j+1)+1;
	return dp[i][j]=max(lcs(i+1,j),lcs(i,j+1));
}

int main(){
	int n;
	cin>>n;
	for(int i=0;i<n;i++){
		s1.clear();s2.clear();
		for(int j=0;j<MAX_N;j++)fill(dp[j],dp[j]+MAX_N,-1);
		cin>>s1>>s2;
		cout<<lcs(0,0)<<endl;
	}
}

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 << lcs(X, Y) << endl;
  }

  return 0;
}

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

int longestCommonSubsequence(string X, string Y) {
	int DP_memory[1000+1][1000+1]; //0~length??????

	for (unsigned int i = 0; i <= X.length(); i++)
		DP_memory[i][0] = 0;
	for (unsigned int i = 0; i <= Y.length(); i++)
		DP_memory[0][i] = 0;

	for (unsigned int i = 1; i <= X.length(); i++) {
		for (unsigned int j = 1; j <= Y.length(); j++) {
			if (X[i] == Y[j])
				DP_memory[i][j] = DP_memory[i - 1][j - 1] + 1;
			else if (DP_memory[i - 1][j] >= DP_memory[i][j - 1])
				DP_memory[i][j] = DP_memory[i - 1][j];
			else
				DP_memory[i][j] = DP_memory[i][j - 1];
		}
	}
	return DP_memory[X.length()][Y.length()];
}

int main() {
	string lcsX[1000];
	string lcsY[1000];
	int setNum;

	cin >> setNum;
	for (int i = 0; i < setNum; i++) {
		cin >> lcsX[i];
		cin >> lcsY[i];

		int lcs = longestCommonSubsequence(lcsX[i], lcsY[i]);
		cout << lcs << endl;
	}
	return 0;
}

C++: #include <iostream>

using namespace std;

int lcs(string X, string Y) {
  int memo[1010][1010];
  int m = X.size();
  int n = Y.size();
  X = ' ' + X;
  Y = ' ' + Y;
  for (int i = 0; i < m; i++) {
    memo[i][0] = 0;
  }
  for (int j = 0; j < m; j++) {
    memo[0][j] = 0;
  }
  int max_lcs = 0;
  for (int i = 1; i <= m; i++) {
    for (int j = 1; j <= n; j++) {
      if (X[i] == Y[j]) {
        memo[i][j] = memo[i-1][j-1] + 1;
      } else {
        memo[i][j] = max(memo[i][j-1], memo[i-1][j]);
      }
      max_lcs = max(max_lcs, memo[i][j]);
    }
  }
  return max_lcs;
}

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<iostream>
#include<map>
#include<deque>
#include<algorithm>
#include<string>
#include<cctype>
using namespace std;
#define REP(i,b,e) for(int i=(int)b;i<(int)e;i++)
#define Rep(i,n) REP(i,0,n)
typedef long long ll;

int q;
string X,Y;
int c[1003][1003];


int main(){
    cin>>q;
    Rep(i,q){
        cin>>X>>Y;
        int m,n;
        int maxl=0;
        m=X.size();
        n=Y.size();
        Rep(j,m+1) c[j][0]=0;
        Rep(k,n+1) c[0][k]=0;
        REP(j,1,m+1){
            REP(k,1,n+1){
                if(X[j]==Y[k]) 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]);
            }
        }
        cout<<maxl<<endl;
    }
    return 0;
}