Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

//Util
func nextStr() string {
	sc.Scan()
	return sc.Text()
}

func nextInt() int {
	sc.Scan()
	i, e := strconv.Atoi(sc.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func maxInt(a, b int) int {
	if a > b {
		return a
	} else {
		return b
	}
}

func minInt(a, b int) int {
	if a > b {
		return b
	} else {
		return a
	}
}

func absInt(a int) int {
	if a >= 0 {
		return a
	} else {
		return -a
	}
}

func absFloat64(a float64) float64 {
	if a >= 0 {
		return a
	} else {
		return -a
	}
}

func minFloat64(a, b float64) float64 {
	if a > b {
		return b
	} else {
		return a
	}
}

func str2Int(s string) int {
	n, _ := strconv.Atoi(s)
	return n
}

//Main
var sc = bufio.NewScanner(os.Stdin)
var q int
var X, Y string

func lcs(X, Y string) int {
	lenX := len(X)
	lenY := len(Y)
	dp := make([][]int, lenX+1)
	for i := 0; i < lenX+1; i++ {
		dp[i] = make([]int, lenY+1)
	}

	res := 0
	for i := 1; i < lenX+1; i++ {
		for j := 1; j < lenY+1; j++ {
			if X[i-1] == Y[j-1] {
				dp[i][j] = dp[i-1][j-1] + 1
			} else {
				dp[i][j] = maxInt(dp[i-1][j], dp[i][j-1])
			}
			//fmt.Println(dp)
			res = maxInt(res, dp[i][j])
		}

	}
	return res
}

func main() {
	sc.Split(bufio.ScanWords)
	q = nextInt()

	for i := 0; i < q; i++ {
		X = nextStr()
		Y = nextStr()

		fmt.Println(lcs(X, Y))
	}
}

C++: #include <iostream>
#include <sstream>
#include <cstdio>
#include <cmath>
#include <cctype>
#include <string>
#include <vector>
#include <list>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <algorithm>
#include <functional>

using namespace std;
using ll = long long int;
#define rep(i,n) for(int i = 0; i < n; i++)
#define FOR(i, a, b)  for(int i = (a); i < (b) ; i++)
#define pb push_back
#define SORT(v,n) sort(v, v+n)
#define ALL(x) (x).begin(),(x).end()
#define debug(x) cerr << #x << ": " << x << '\n'
#define elif else if
#define itn ll
#define int ll
const int INF = 100100100;
const int MOD = (int)1e9 + 7;
const double EPS = 1e-9;
///                →,↑,←,↓,↗,↖,↙,↘
int dx[8] = { 1, 0, -1, 0, 1, -1, -1, 1 };
int dy[8] = { 0, 1, 0, -1, 1, 1, -1, -1 };


static const int N = 1000;

int lcs(string X, string Y) {
	int c[N + 1][N + 1];
	int maxl = 0;
	int i, j;
	int m = X.size();
	int n = Y.size();
	X = ' ' + X;
	Y = ' ' + Y;
	FOR(i, 1, m+1) {
		c[i][0] = 0;
	}
	FOR(i, 1, n+1) {
		c[0][i] = 0;
	}
	for (int i = 1; i <= m; i++) {
		for (int j = 1; j <= n; j++) {
			if (X[i] == X[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(c[i][j], maxl);
		}
	}
	return maxl;
}

signed main() {
	ios::sync_with_stdio(false);
	int n;
	string s1, s2;
	cin >> n;
	int i;
	rep(i, n) {
		cin >> s1 >> s2;
		cout << lcs(s1, s2) << "\n";
	}
	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 x, y;
  int n;
  cin >> n;
  for(int i = 0 ; i < n ; i++){
    cin >> x >> y;
    cout << lcs(x,y) << endl;
  }
return 0;

}

C++: #include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<n;++i)
#define rep1(i,n) for(int i=1;i<=n;++i)
#define eachdo(e,array) for(const auto& e : array)
#define lower_index(v,a) (int)distance(v.begin(), lower_bound((v).begin(),(v).end(),a))
template<class T> bool chmin(T &a, T b){if(a>b){a=b;return true;}return false;}
template<class T> bool chmax(T &a, T b){if(a<b){a=b;return true;}return false;}
typedef long long ll;
const int inf = 1<<28;
const ll INF = 1LL<<57;
const ll MOD = 1e9+7;

int main(){ 
    ll N; cin >> N;
    rep(_,N){
        string x,y;cin >> x >> y;
        ll X = x.size();
        ll Y = y.size();
        vector<vector<ll>> dp(X+1,vector<ll>(Y+1,0));
        rep(i,X)rep(j,Y){
            if (x[i]==y[j]) chmax(dp[i+1][j+1],dp[i][j]+1);
            else chmax(dp[i+1][j+1],max(dp[i+1][j],dp[i][j+1]));
        }
        cout << dp[X][Y] << endl;
    }

}

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

struct node{
  int value;
  node *next;
  node(int value, node *next):value(value),next(next){};
};
#define INF ( 1 << 28 )
string lcs(string &a, string &b){
  map< int , vector< int > > M;
  for(int i = b.size() - 1 ; i >= 0 ; i--){
    M[b[i]].push_back(i);
  }
  vector<int > HM(a.size() + 1, INF);
  HM[0] = -INF;
  vector<node*> link(a.size() + 1);
  for(int i = 0 ; i < a.size() ; i++ ){
    if(M.count(a[i])){
      vector< int > NEWHM = M[a[i]];
      for(int j = 0 ; j < NEWHM.size() ; j++ ){
        int k = distance( HM.begin(), lower_bound( HM.begin(), HM.end(), NEWHM[j]));
        HM[k] = NEWHM[j];
        link[k] = new node( b[NEWHM[j]], link[k - 1]);
      }
    }
  }
  string ans;
  for(node* p = link[distance(HM.begin(),lower_bound(HM.begin(),HM.end(),INF-1))-1];p;p = p->next){
    ans += (char)p -> value;
  }
  reverse(ans.begin(), ans.end());
  return ans;
}
int main(){
  int q;
  cin >> q;
  while(q--){
    string a, b;
    cin >> a >> b;
    string ans = lcs( a, b);
    cout << ans.size() << endl;
  }
}

C++: #include<iostream>
#include<string>
#include<algorithm>
using namespace std;
 
int lcs(string x, string y) {
    static int c[1001][1001];
    int m = x.size();
    int n = y.size();
    int max1 = 0;
    x = ' ' + x;
    y = ' ' + y;
    for (int i = 0; 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]);
            max1 = max(max1, c[i][j]);
 
        }
    }
    return max1;
}
 
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 <stdio.h>
#include <string.h>
#define N 1000

void Ics(char *X, char *Y)
{
   int c[N][N];
   int m, n, i, j;

   m = strlen(X);
   n = strlen(Y);

   for ( i = 0; i <= m; i++ ) {
      c[i][0] = 0;
   }
   for ( j = 1; j <= n; j++ ) {
      c[0][j] =0;
   }

   for ( i = 1; i <= m; i++ ) {
      for ( j = 1; j <=n; 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 ];
         }
      }
   }
   printf("%d\n", c[ m ][ n ]);
}
     
int main()
{
   int n, i;
   char X[N], Y[N];

   scanf("%d", &n);
   for ( i = 0; i < n; i++ ) {
      scanf("%s%s", X, Y);
      Ics(X, Y);
   }
   return 0;
}

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

using namespace std;

const int MAXN = 1010;

int main(int argc, char const *argv[]) {
  int q;
  cin >> q;
  for (auto k = 0; k < q; k++) {
    vector<vector<int>> dp(MAXN, vector<int>(MAXN, 0));
    string s1, s2;
    cin >> s1 >> s2;
    auto n = s1.size();
    auto m = s2.size();
    for (size_t i = 0; i < n; i++) {
      for (size_t j = 0; j < m; j++) {
        if (s1[i] == s2[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[n][m] << endl;
  }

  return 0;
}