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 <string>
using namespace std;
int main(void){
   long L[1010][1010], Z; 
   string X, Y; 
   int q;  
    cin >> q; 
  for(int k=0; k<q; k++){ 
      cin >> X;  
      cin >> Y; 
      for(int i=0; i<X.size(); i++){   
            for(int j=0; j<Y.size(); j++){
           L[i][j] = 0;
            }
      }
      for(int i=0; i<X.size(); i++){
       for(int j=0; j<Y.size(); j++){
           if(i<=0 || j<=0){
               if(X[i]==Y[j])  L[i][j]=1;
               else            L[i][j]=0;
           }
           else if(X[i] == Y[j])
                L[i][j]=1+L[i-1][j-1];
           else L[i][j]=max(L[i][j-1], L[i-1][j]); 
          Z=L[i][j];
       } 
     } 
     cout << Z << endl;
  }
   return 0;
}

C++: #include <iostream>
#include <string>
#include <algorithm>
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 <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <map>
#include <set>
#include <vector>
#include <stack>
#include <queue>
#include <bitset>
#include <algorithm>
#include <numeric>
#include <functional>
using namespace std;

#define Rep(b, e, i) for(int i = b; i <= e; i++)
#define Repr(e, b, i) for(int i = e; i >= b; i--)
#define rep(n, i) Rep(0, n-1, i)
#define repr(n, i) Repr(n-1, 0, i)
#define all(v) (v).begin(), (v).end()
#define pb(x) push_back(x)
#define uniq(x) (x).erase(unique(all(x)),(x).end())

typedef long long ll;

const int MAX = 1024;
const int INF = 1<<29;

ll dp[MAX][MAX];

ll LCS(string s, string t) {
    memset(dp, 0LL, sizeof(dp));
    int sl = (int)s.size(), tl = (int)t.size();
    rep(sl, i) rep(tl, j) {
        if (s[i] == t[j]) dp[i+1][j+1] = dp[i][j]+1;
        else dp[i+1][j+1] = max(dp[i+1][j], dp[i][j+1]);
    }
    return dp[sl][tl];
}

void solve(void){
    int N;
    cin >> N;
    rep(N, i) {
        string s, t;
        cin >> s >> t;
        cout << LCS(s, t) << endl;
    }
}

int main(void){
  solve();
  //cout << "yui(*-v・)yui" << endl;
  return 0;
}

C++: #include<iostream>
#include<vector>
#include<string>
#include<cmath>
#include<algorithm>
int main(){
  int q;
  std::cin>>q;
  std::vector<std::string> str1,str2;
  std::string str;
  for(int i=0;i<q;i++){
    std::cin>>str;
    str1.push_back(str);
    std::cin>>str;
    str2.push_back(str);
    //std::cout<<str1[i][0]<<"\n";
    //std::cout<<str2[i][0]<<"\n";
  }
  
 
  for (int i = 0; i < q; i++) {
	  int ans[str1[i].length()+1][str2[i].length()+1];
	  for (int j = 0; j < str1[i].length() + 1; j++) {
		  for (int k = 0; k < str2[i].length() + 1; k++) {
			  
			  if (j == 0 || k == 0) {
				  ans[j][k] = 0;
			  }else {
				  //std::cout << " str1= " << str1[i][j-1] << " str2= " << str2[i][k-1] << " \n ";
				  if (str1[i][j-1] == str2[i][k-1]){
					  //std::cout << "ppp";
					  ans[j][k] = std::max({ ans[j - 1][k - 1] + 1,ans[j - 1][k],ans[j][k - 1] });
					  //ans[j][k] = std::max({ 1,2,3 });
				  }else {
					  ans[j][k] = std::max(ans[j - 1][k], ans[j][k - 1]);
				  }
			  }
			  //std::cout << ans[j][k] << " ";
			  
		  }
		  //std::cout << "\n";
	  }
	  std::cout << ans[str1[i].length()][str2[i].length()] << "\n";
  }
  

  return 0;
}

C++: /*
* @Author: Samson
* @Date:   2018-06-11 11:31:19
* @Last Modified by:   Samson
* @Last Modified time: 2018-06-11 11:46:49
*/
//   @URL : http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_10_C
#include<bits/stdc++.h>
#include<algorithm>
#include <cstdlib>
#define INF 0x3f3f3f3f
using namespace std;
typedef long long LL;
const int MAXN = 1e3+10;

string a,b;
int f[MAXN][MAXN];

int solve()
{
	memset(f,0,sizeof f);
	int lena = a.size(),lenb = b.size();
	int maxv = 0;
	a = ' '+a,	b = ' '+b;
	for(int i = 1; i <= lena; ++i)
	{
		for(int j = 1; j <= lenb; ++j)
		{
			if(a[i] == b[j])
				f[i][j] = f[i-1][j-1]+1;
			else
				f[i][j] = max(f[i-1][j],f[i][j-1]);
			if(f[i][j] > maxv)	maxv = f[i][j];
		}
	}
	return maxv;
}
int main(void)
{
	ios::sync_with_stdio(false); 
	//cin.tie(0);
	int T;
	cin>>T;
	while(T--)
	{
		cin>>a>>b;
		cout<<solve()<<'\n';
	}
	return 0;
}

C++: #include <algorithm>
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(x) (x).begin(), (x).end()
#define ll long long
#define ld long double
#define INF 1000000000000000000
typedef pair<ll, ll> pll;
typedef pair<int, int> pint;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int N;
    cin >> N;
    rep(i, N) {
        string s, t;
        cin >> s >> t;
        int N = s.size(), M = t.size();
        vector<vector<int>> dp(N + 1, vector<int>(M + 1));

        rep(i, N) {
            rep(j, M) {
                if (s[i] == t[j])
                    dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i][j] + 1);
                dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i][j + 1]);
                dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i + 1][j]);
            }
        }

        cout << dp[N][M] << endl;
    }
}