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 <cstdio>
#include <cstdlib>
#include <cassert>
#include <string>
#include <cstring>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>

using namespace std;

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

// debug
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;

// ---------------------
#define INF 922337203685477580
typedef long long ll;

int dp[1010][1010];

int main() {
  int q;
  cin >> q;
  REP(loop, q) {
    char S[1000], T[1000];
    cin >> S >> T;

    REP(i, strlen(S)) {
      REP(j, strlen(T)) {
        dp[i][j] = 0;
      }
    }
    for (int i = 0; i < strlen(S); i++) {
      for (int j = 0; j < strlen(T); 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]);
        }
      }
    }
    cout << dp[strlen(S)][strlen(T)] << 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 <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <string>
#include <sstream>
#include <algorithm>
#include <iomanip>
#include <iostream>

#define VARIABLE(x) cerr << #x << "=" << x << endl
#define BINARY(x) static_cast<bitset<16> >(x);
#define if_range(x, w, h) if (w <= x && x <= h)
#define BitCheck(a,b)   (a >> b) & 1
#define BitSet(a,b)       a |= (1 << b)
#define BitunSet(a,b)    a &= ~(1 << b)

int compare_int(const void* a, const void* b) { return *(int*) a - *(int*) b; }

int main() {
	int n, m, a, dp[102][102] = { 0 };
	char s[1001], t[1001];
	scanf("%d", &a);
	for (int k = 0; a > k; k++) {
		scanf("%d %d %s %s", &n, &m, s, t);
		for (int i = 1; n >= i; i++) {
			for (int j = 1; m >= j; j++) {
				if (s[i - 1] == t[j - 1])dp[i][j] = dp[i - 1][j - 1] + 1;
				else dp[i][j] = __max(dp[i - 1][j], dp[i][j - 1]);
			}
		}
		printf("%d\n", dp[n][m]);
	}
	return 0;
}

C++: #include <iostream>
#include <sstream>
#include <vector>
#include <algorithm>
#include <string>
#include <functional>
#include <numeric>
#include <ctype.h>
#include <cstdlib>
#include <string.h>
#include <cmath>
#include <cstdio>
#include <map>
#include <queue>
#include <utility>
#define rep(i, n) for(int i = 0; i < n; i++);

using namespace std;

const int INF = 1000000007;
const double PI = acos(-1.0);
typedef long long llong;

const int N = 10000;

int search(string X, string Y)
{
	int c[1000 + 1][1000 + 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 input1, input2;
	int n;
	cin >> n;
	for (int i = 0; i < n; i++)
	{
		cin >> input1 >> input2;
		cout << search(input1, input2) << endl;
	}

	return 0;
	

}

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

string X;
string Y;

int calc(int x_s, int x, int y, int length){
    if (X[x] == '\0') return length;
    int y_ = Y.find(X[x], y);
    if (y_ == string::npos) {
        return max(length, calc(x_s + 1, x_s + 1, 0, 0));
    }
    return calc(x_s, x + 1, y_ + 1, length + 1);
}

int main(){
    int q;
    cin >> q;
    for (int i = 0; i < q; i++) {
        cin >> X;
        cin >> Y;
        cout << calc(0, 0, 0, 0) << endl;
    }

    return 0;
}

C++: #include <stdio.h>
#include <string.h>

int main(){
   char str_s[128], str_p[128];
   int a[100]=0;
   int i, j, c, h, n, m;
   scanf("%d",n);
   for(i=0;i < n;i++){
      scanf("%s",str_s);
      scanf("%s",str_p);
      n=strlen(str_s);
      m=strlen(str_p);
      c=0;
      h=0;
      for(i=0;i < n;i++){
         for(j=h;j < m;j++){
            if(str_s[i] ==str_p[j]){
               h=j+1;
               c++;
               break;
            }
         }
      }
      printf("%d\n, c");
   }

   return 0;
}

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

int main(){
  int i,j,n,c[1001][1001];
  string x,y;
  cin >> n;
  while(n>0){
    n--;
    cin >> x;
    cin >> y;

    int lenx = x.size();
    int leny = y.size();

    for(i = 1; i < lenx; i++){
      c[i][0] = 0;
    }
    for(j = 1; j < leny; j++){
      c[0][j] = 0;
    }
  
    for(i = 0; i < lenx; i++){
      for(j = 0; j < leny; 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];
	}
      }
    }
    cout << c[lenx-1][leny-1] << endl;
  }
  return 0;
}