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>
#include <cstring>
using namespace std;

int q;
int **len;
int common(string a,string b,int m,int n){
    if(m==0||n==0){
        return 0;
    }
    if(a[m-1]==b[n-1]){
        if(m>1&&n>1){
            if(len[m-2][n-2]!=-1)len[m-1][n-1]=len[m-2][n-2]+1;
            else len[m-1][n-1]=common(a.substr(0,m-1),b.substr(0,n-1),m-1,n-1)+1;
        }else{
            len[m-1][n-1]=1;
        }
    }
    else{
        int l1,l2;
        //?±?l1
        if(n>1){
            if(len[m-1][n-2]!=-1)l1=len[m-1][n-2];
            else l1=len[m-1][n-2]=common(a,b.substr(0,n-1),m,n-1);
        }else l1=-1;
        if(m>1){
            if(len[m-2][n-1]!=-1)l2=len[m-2][n-1];
            else l2=len[m-2][n-1]=common(a.substr(0,m-1),b,m-1,n);
        }else l2=-1;

        len[m-1][n-1]=max(l1,l2);
    }
    return len[m-1][n-1];
}

int main()
{
    cin>>q;
    int i;
    for(i=0;i<q;i++){
        string a,b;
        cin>>a>>b;
        int m=a.length();
        int n=b.length();
        len=new int*[m];
        int j;
        for(j=0;j<m;j++){
            len[j]=new int[n];
            memset(len[j],-1,n*sizeof(int));
        }
        cout<<common(a,b,m,n)<<endl;
    }
    return 0;
}

//int main(){
//    int **p=new int*[5];
//    p[1]=new int[5];
//    memset(p[1],-1,5*sizeof(int));
//    cout<<p[1][3]<<" "<<p[0][1];
//}

C++: #include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); ++i)
using namespace std;
typedef long long ll;

int c[2000][2000];

int lcs(string X, string Y){
    int x = X.length();
    int y = Y.length();
    rep(i, x){
        c[i][0] = 0;
    }
    rep(i, y){
        c[0][i] = 0;
    }
    for (int i = 1; i <= x; i++){
        for (int j = 1; j <= y; j++){
            if(X[i-1] == Y[j-1]){
                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[x][y];
}

int main() {
    int q; cin >> q;
    rep(i, q){
        string X, Y; cin >> X >> Y;
        int ans = lcs(X, Y);
        cout << ans << endl;
    }

    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define For(I,A,B) for(int I=(A); I < (B); ++I)
int c[1005][1005];
int main()
{
int t;
string p;
cin>>t;
getline(cin,p);
while(t--){

int x,y,z,k=0,l,i,j;
string a,b,q="o",r="o";

 For(i,0,1005)
 For(j,0,1005)
 c[i][j]=0;

 getline(cin,a);
 getline(cin,b);
 x=a.length();
 y=b.length();

  For(i,0,x) q=q+a[i];

  For(i,0,y) r=r+b[i];
 For(i,1,x+1)
 For(j,1,y+1)
 {
     if(q[i]==r[j]) 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][y]<<endl;

}

    return 0;
}

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

using namespace std;
const int N_MAX = 1000;
char x[N_MAX+10], y[N_MAX+10];
int dp[N_MAX][N_MAX];

void solve() {
  int i, j;
  scanf("%s", x);
  scanf("%s", y);
  int N = strlen(x);
  int M = strlen(y);
  //printf("N = %d M = %d", N, M);
  for (i = 0; i < N+1; i++) {
    dp[i][0] = 0;
  }
  for (j = 0; j < M+1; j++) {
    dp[0][j] = 0;
  }
  for (i = 0; i < N; i++) {
    for (j = 0; j < M; j++) {
      if (x[i] == y[j]) {
	dp[i+1][j+1] = dp[i][j]+1;
      } else {
	dp[i+1][j+1] = max(dp[i][j+1], dp[i+1][j]);
      }
    }
  }
  printf("%d\n", dp[N][M]);
} 

int main() {
  int q;
  scanf("%d", &q);
  for (int i = 0; i < q; i++) {
    solve();
  }
  return 0;
}

C++: #include<iostream>
#include<string>
#define lth 1000

using namespace std;

int main()
{
	int n, L[100][100], Lmax = 0, *save;
	string *Xi, *Yi;
	cin >> n;
	save = new int[n];
	if (n <= 20)
	{
		Xi = new string[lth];
		Yi = new string[lth];
	}
	else
	{
		Xi = new string[100];
		Yi = new string[100];
	}
	for (int k = 0; k < n; k++)
	{
		Lmax = 0;
		string X, Y;
		cin >> X >> Y;
		for (int i = 0; i <= X.length(); i++)
		{
			if (i != 0)
				Xi[i] = X.substr(0, i );
		}
		for (int i = 0; i <= Y.length(); i++)
		{
			if (i != 0)
				Yi[i] = Y.substr(0, i );
		}
		for (int i = 0; i <= X.length(); i++)
			for (int j = 0; j <= Y.length(); j++)
			{
				if (i == 0 || j == 0)
					L[i][j] = 0;
				else if (Xi[i][i - 1] == Yi[j][j - 1])
				{
					L[i][j] = L[i - 1][j - 1] + 1;
				}
				else
				{
					L[i][j] = (L[i][j - 1] > L[i - 1][j]?L[i][j - 1] : L[i - 1][j]);
				}
				if (Lmax < L[i][j]) Lmax = L[i][j];
			}
		save[k] = Lmax;
	}
	for (int i = 0; i < n; i++)
		cout << save[i] << endl;
	//system("pause");
}

C++: #include <iostream>
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];

      max = (max < dp[i][j]) ? dp[i][j] : max;
    }
  }

  return max;
}

int main() {
  int N = 0;
  cin >> N;

  for (int i = 0; i < N; i++) {
    string X, Y;
    cin >> X >> Y;

    cout << lcs(X, Y) << '\n';
  }

  return 0;
}