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 <climits>
using namespace std;

long int dp[10000][10000];
string  s1, s2;
void solve(){
  for(int i=0;i<=max(s1.size(),s2.size())+1;i++){
     dp[i][i]=0;
  }
  int val;
  for(int x=1;x<=s1.size();x++){
    for(int y=1;y<=s2.size();y++){
	  if(s1[x]==s2[y]){
	    val = max(dp[x-1][y-1]+1,max(dp[x-1][y],dp[x][y-1]));
	  }else{
	    val = max(dp[x-1][y-1],max(dp[x-1][y],dp[x][y-1]));
          }
          dp[x][y] = val;
    }
  }/*
    for(int x=1;x<=s1.size();x++){
    for(int y=1;y<=s2.size();y++){
      cout<<dp[x][y]<<" ";
    }
    cout<<endl;
    }*/
    cout<<dp[s1.size()][s2.size()]<<endl;
}

int main(){ 
  int n;
   cin>>n;
   for(int i=0; i<n; i++){
      cin>>s1>>s2;
      solve();
   }
   return 0;
}

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

using namespace std;

int LCS(string a, string b);
int S[1001][1001];

int main() {
    int n;
    cin >> n;
    string a, b;

    vector<int> ans;
    
    for (int i = 0; i < n; i++) {
        cin >> a;
        cin >> b;
        ans.push_back(LCS(a, b));
    }
    for (int i = 0; i < n; i++) {
        cout << ans[i] << '\n';
    }
}

int LCS(string a, string b) {

    int len_a = a.size();
    int len_b = b.size();
    for (int i = 1; i <= len_a; i++) {
        for (int j = 1; j <= len_b; j++) {
            if (a[i-1] == b[j-1]) S[i][j] = S[i-1][j-1] + 1;
            else {
                S[i][j] = max(S[i][j-1], S[i-1][j]);
            }
        }
    }

    return S[len_a][len_b];
}

C++: #include<iostream>
#include<stdio.h>
//#include <bits/stdc++.h>
#include<vector>
#include<float.h>
#include<iomanip>
#include<algorithm>
#include<string>
#include<cstring>
#include<math.h>
#include<cmath>
#include<sstream>
#include<set>
#include<map>
#include<queue>
#include <cassert>
#include <cmath>
#include<cstdint>

#define INF 1e9
#define rep(i,n)for(int i=0;(i)<(int)(n);i++)
#define REP(i,a,b)for(int i=(int)(a);(i)<=(int)(b);i++)
#define VEC(type, c, n) std::vector<type> c(n);for(auto& i:c)std::cin>>i;
#define vec(type,n) vector<type>(n)
#define vvec(m,n) vector<vector<int>> (int(m),vector<int>(n))
#define ALL(a)  (a).begin(),(a).end()

using namespace std;
using ll = long long;
using Graph = vector<vector<int>>;
using P = pair<int,int>;

vector<int>bitSearch(int bit,int n){
    vector<int>S;
    rep(i,n)if(bit&(1<<i))S.push_back(i);
    return S;
}

int main(){
    int q;
    while(cin>>q){
        rep(i,q){
            string s,t;cin>>s>>t;
            int m = s.size(),n = t.size();
            s.insert(0,"0");
            t.insert(0,"0");
            int dp[m+1][n+1];
            rep(j,m+1)rep(k,n+1)dp[j][k] = 0;
            REP(j,1,m){
                REP(k,1,n){
                    if(s[j] == t[k]){
                        dp[j][k] = max({dp[j][k],dp[j-1][k-1]+1,dp[j-1][k],dp[j][k-1]});
                    }
                    else dp[j][k] = max({dp[j][k],dp[j-1][k],dp[j][k-1]});
                }
            }
            cout<<dp[m][n]<<endl;
        }
    }
}

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

int main(int argc, char const *argv[]) {
        int x; cin>>x;

        while (x--) {
                string s,t; cin>>s>>t;
                int n = s.length(); int m = t.length();
                vector<vector<int> > dp(n+1, vector<int>(m+1, 0));
                for (int i = 1; i <= n; ++i) {
                        for (int j = 1; j <= m; j++) {
                                if (s[i-1]==t[j-1]) dp[i][j] = max(dp[i][j], dp[i-1][j-1]+1);
                                else {
                                        dp[i][j] = max(dp[i][j], max(dp[i-1][j], dp[i][j-1]));
                                }
                        }
                }
                cout << dp[n][m] << endl;
        }

        return 0;
}

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

int main() {
  int q; cin >> q;
  string A, B; cin >> A >> B;
  for (int i=0; i<q; i++) {
    vector<vector<int>> LCS(A.length()+1, vector<int>(B.length()+1,0));
    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]);
      }
    }
    cout << LCS[A.length()][B.length()]
  }
}

C++: #include <bits/stdc++.h>
using namespace std;
long long dp[1002][1002];
int main() {
  int n;cin>>n;
  for(int i=0; i<n; i++){
  
  string a,b; cin>>a>>b;
  int al=a.size(); int bl=b.size();
  for (int i=0;i<1002;i++){for(int j=0;j<1002;j++){dp[i][j]=0;}}
  for (int j=0;j<al;j++){
  for (int k=0;k<bl;k++){
  if(a[j]==b[k]){dp[j+1][k+1]=dp[j][k]+1;}
  else{dp[j+1][k+1]=max(dp[j+1][k],dp[j][k+1]);}
  }
  }
  cout << dp[al][bl] << endl;
  }
}

C++: #include<iostream>
#include<vector>
#include<string>
using namespace std;
string s1,s2;
int memo[100][100];

int solve(int l1,int l2){
  if(memo[l1][l2] < 0)return memo[l1][l2];
  if(l1 < 0 or l2 < 0)return 0;
  //cout << s1[l1] << s2[l2] << endl;
  if(s1[l1] == s2[l2]){
    return memo[l1][l2] = solve(l1 - 1,l2 - 1) + 1;
  }
  return memo[l1][l2] = max(solve(l1,l2-1), solve(l1-1,l2));
}
int main(){
  int n;
  cin >> n;
  for(int i = 0;i < n;i++){
    fill(*memo,*(memo+100),-1);
    cin >> s1 ;
    cin >> s2;
    cout << solve(s1.length(),s2.length()) - 1 << endl;
  }
}