Go: package main

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

// define
var (
	sc = bufio.NewScanner(os.Stdin)
)

func bordersInt(in_map [][]int, invalid int) [][]int{
	H, W := len(in_map), len(in_map[0])
	out_map := make([][]int, H+2)
	for h:=0; h<H+2; h++ {
		out_map[h] = make([]int, W+2)
		for w:=0; w<W+2; w++ {
			out_map[h][w] = invalid
		}
	}
	for h:=0; h<H; h++{
		for w:=0; w<W; w++{
			out_map[h+1][w+1] = in_map[h][w] 
		}
	}
	return out_map
}

func bordersString(in_map [][]string, invalid string) [][]string{
	H, W := len(in_map), len(in_map[0])
	out_map := make([][]string, H+2)
	for h:=0; h<H+2; h++ {
		out_map[h] = make([]string, W+2)
		for w:=0; w<W+2; w++ {
			out_map[h][w] = invalid
		}
	}
	for h:=0; h<H; h++{
		for w:=0; w<W; w++{
			out_map[h+1][w+1] = in_map[h][w] 
		}
	}
	return out_map
}

func scanIntLine(len int) []int{
	arr := make([]int, len)
	for i:=0; i<len; i++{
		sc.Scan()
		tmp, err := strconv.Atoi(sc.Text())
		if err == nil{
			arr[i] = tmp
		}
	}
	return arr
}

func scanStringLine(len int) []string{
	arr := make([]string, len)
	for i:=0; i<len; i++{
		sc.Scan()
		arr[i] = sc.Text()
	}
	return arr
}

func scanIntSplit(len int) []int{
	arr := make([]int, len)
	sc.Scan()
	for i, v := range strings.Split(sc.Text(), " "){
		tmp, err := strconv.Atoi(v)
		if err == nil{
			arr[i] = tmp
		}
	}
	return arr
}

func maxInt(args... int) int{
	sort.Ints(args)
	return args[len(args)-1]
}

func main(){
	buf := make([]byte, 0)
    sc.Buffer(buf, 1000000009)
	var n int 
	fmt.Scan(&n)
	dp := make([][]int, 1003)
	for i:=0; i<1003; i++ {
		dp[i] = make([]int, 1003)
	}
	input_lines := scanStringLine(2*n)
	for i:=0; i<n; i++ {
		S, T := input_lines[2*i], input_lines[2*i+1]
		lenS, lenT := len(S), len(T)
		for i:=1; i<lenS+1; i++ {
			for j:=1; j<lenT+1; j++ {
				if S[i-1] == T[j-1] {
					dp[i][j] = dp[i-1][j-1]+1
				} else if S[i-1] != T[j-1] && dp[i-1][j] > dp[i][j-1] {
					dp[i][j] = dp[i-1][j]
				} else {
					dp[i][j] = dp[i][j-1]
				}
				// if S[i-1] == T[j-1] {
				// 	dp[i][j] = maxInt(dp[i-1][j-1]+1, dp[i-1][j], dp[i][j-1])
				// } else {
				// 	dp[i][j] = maxInt(dp[i-1][j], dp[i][j-1])
				// }
			}
		}
		fmt.Println(dp[lenS][lenT])
	}
}

C++: #include <bits/stdc++.h>
#define int long long
#define double long double
#define rep(i, a, n) for(int i = (int)(a);(i) < (int)(n);++(i))
#define repe(i, a, n) for(int i = (int)(a);(i) <= (int)(n);++(i))
#define repif(i, a, x) for(int i = (int)(a);(x);++(i))
#define repr(i, a, n) for(int i = ((int)(a)-1);(i) >= (int)(n);--(i))
#define reper(i, a, n) for(int i = (int)(a);(i) >= (int)(n);--(i))
#define SZ(x) ((int)(x).size())
#define ALL(x) begin(x), end(x)
#define CEIL(x) ((int)ceil(((double)x)))
#define POW(x, y) ((int)pow(x, y))
#define UNIQUE(x) (x).erase(unique(ALL((x))), end(x))
#define gcd(x, y) __gcd(x, y)
#define lcm(x, y) ((x)/gcd(x,y)*(y))
#define isin(x, l, r) ((l) <= (x) and (x) < (r))
#define fcout(n) cout << fixed << setprecision(n)
#define rcout(n) cout << right << setw(n)
#define pb push_back
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound
#define PI (acosl(-1))
#define EPS (1e-10)
#define INF LLONG_MAX
#define INF32 INT32_MAX
#define MOD 1000000007LL
using namespace std;
using VI = vector<int>;
using PII = pair<int, int>;
using TIII = tuple<int, int, int>;
using VPII = vector<PII>;
using VTIII = vector<TIII>;
using Complex = complex<double>;
template<typename T, template<typename> typename C = less> using PQ = priority_queue<T, vector<T>, C<T>>;
template<typename T> inline bool chmax(T& a, const T& b, bool t = false){ if(a<b or (t and a == b)){ a=b; return true; } return false; }
template<typename T> inline bool chmin(T& a, const T& b, bool t = false){ if(a>b or (t and a == b)){ a=b; return true; } return false; }


signed main(){
    int q;
    cin >> q;
    while(q--){
        string X, Y;
        cin >> X >> Y;
        vector<VI> dp(SZ(X)+1, VI(SZ(Y)+1));
        rep(i, 0, SZ(X)) rep(j, 0, SZ(Y)){
            if(X[i] == Y[j]) 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[SZ(X)][SZ(Y)] << endl;
    }

    return 0;
}

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

#define NUM 1000
int dp[NUM + 1][NUM + 1];

void calc(string X, string Y){
    for(int i = 0; i <= X.size(); i++){
        for(int j = 0; j <= Y.size(); j++){
            dp[i][j] = 0;
        }
    }

    for(int j = 1; j <= Y.size(); j++){
        for(int i = 1; i <= X.size(); i++){
            if(X[i - 1] == Y[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[X.size()][Y.size()]);

}

int main(void){
    int q;
    scanf("%d", &q);

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

C++: #include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <map>
#include <queue>
#include <utility>
using namespace std;
//_____
#define pb push_back
#define fi first
#define se second
#define mkp make_pair
#define ALL(x) x.begin(),x.end()
#define rep(i,n) for(int i=0; i<(n); ++i)
#define reps(i,f,n) for(int i=(f); i<=(n); ++i)
#define err(...) fprintf(stderr, __VA_ARGS__)
#define show(x) cerr << #x << ':' << x << endl
#define outl(x) cout << (x) << '\n'
#define FAST() cin.tie(0), ios::sync_with_stdio(false)
typedef long long ll;
typedef pair<int,int> pii;
template<class A, class B>inline bool chmax(A &a, B b){return b>a ? a=b,1 : 0;}
template<class A, class B>inline bool chmin(A &a, B b){return b<a ? a=b,1 : 0;}
inline bool inside(int y, int x, int H, int W){return(y>=0 && x>=0 && y<H && x<W);}
const int INF = 1 << 29;
const int dx[] = {1, 0, -1, 0,  1, 1, -1, -1};
const int dy[] = {0, 1, 0, -1,  -1, 1, 1, -1};
#define LEN 1000011
#define NIL -1
//_______

int dp[1005][1005];

int slv(string &a, string &b)
{
   const int alen = a.size();
   const int blen = b.size();
   a = ' ' + a;
   b = ' ' + b;
   int ret = 0;
   reps(i, 0, alen)dp[0][i] = 0;
   reps(i, 0, blen)dp[i][0] = 0;

   reps(i, 1, alen){
      reps(j, 1, blen){
         if(a[i] == b[j]){
            dp[i][j] = dp[i-1][j-1] + 1;
         } else {
            dp[i][j] = max(dp[i-1][j] , dp[i][j-1] );
         }
         chmax(ret, dp[i][j]);
      }
   }
   return(ret);
}

signed main()
{
   FAST();
   int N;
   cin >> N;
   rep(i, N){
      string a,b;
      cin >> a >> b;
      outl( slv(a, b) );
   }
}

C++: #include <bits/stdc++.h>

using namespace std;

#define Vi vector<int>
#define FOR(i,s,e) for (int i=s; i<e; i++)
#define ITER(v) v.begin(), v.end()

constexpr int MAX_LEN = 1'000;
int dp[MAX_LEN][MAX_LEN];

void set_val(int i, int j, int inc) {
    int val = inc;
    if (i > 0 && j > 0) {
        int tmp = dp[i-1][j-1] + inc;
        val = max(val, tmp);
    }
    if (i > 0) {
        int tmp = dp[i-1][j] + inc;
        val = max(val, tmp);
    }
    if (j > 0) {
        int tmp = dp[i][j-1] + inc;
        val = max(val, tmp);
    }
    dp[i][j] = val;
}

int lcs(const string& x, const string& y) {
    int lx = x.length();
    int ly = y.length();
    for (int i=0; i<lx; ++i) {
        bool isalreadyinc = false;
        for (int j=0; j<ly; ++j) {
            if (x[i] == y[j] && !isalreadyinc) {
                set_val(i, j, 1);
                isalreadyinc = true;
            } else {
                set_val(i, j, 0);
            }
        }
    }
    return dp[lx-1][ly-1];
}

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

    int n;
    cin >> n;

    string x, y;
    FOR(i,0,n) {
        cin >> x;
        cin >> y;
        cout << lcs(x, y) << endl;
    }

    return 0;
}