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])
	}
}

Python: #!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
input:
3
abcbdab
bdcaba
abc
abc
abc
bc

output:
4
3
2

"""
import sys


def lcs(A, B):
    m, n = len(A), len(B)
    count_list = tuple([[0] * (n + 1) for _ in range(m + 1)])

    for i in range(1, m + 1):
        for j in range(1, n + 1):
            if A[i - 1] == B[j - 1]:
                count_list[i][j] = count_list[i - 1][j - 1] + 1
            else:
                count_list[i][j] = max(count_list[i - 1][j], count_list[i][j - 1])

    return count_list[m][n]


def lcs_better(A, B):
    cost_history = [None]
    for ele in B:
        for index in range(len(cost_history) - 1, -1, -1):
            # ???????¬??????°????????????????§???¨A??\?????°??????(ele), ????????°?????????
            found = A.find(ele, cost_history[index])
            if found != -1:
                if index + 1 < len(cost_history):
                    cost_history[index + 1] = min(cost_history[index + 1], found + 1)
                # ??¨???????????°?????¢?????°?????¶?????°????????´???
                else:
                    # assert index + 1 == len(cost_history)
                    cost_history.append(found + 1)

    return len(cost_history) - 1


if __name__ == '__main__':
    _input = sys.stdin.readlines()
    pair_num = int(_input[0])

    word_list = _input[1:]
    # assert len(word_list) == 2 * pair_num
    for k in range(0, len(word_list), 2):
        print(lcs(word_list[k].strip(), word_list[k + 1].strip()))

Python: import sys
def lcs(X, Y):
    x = len(X) + 1
    y = len(Y) + 1
    c = [0 for y in range(y)]

    for i in range(1, x):
        tmp = c[:]
        for j in range(1, y):
            if X[i - 1] == Y[j - 1]:
                c[j] = tmp[j - 1] + 1
            else:
                c[j] = max(tmp[j], c[j - 1])
    return c[y - 1]

n = int(input())

for i in range(n):
    X = sys.stdin.readline()[:-1]
    Y = sys.stdin.readline()[:-1]
    print(lcs(X, Y))

Python: for _ in[0]*int(input()):
 X,z=input(),[]
 for y in input():
  s=i=0
  for k in z:
   t=X.find(y,s)+1
   if t<1:break
   if t<k:z[i]=t
   s=k;i+=1
  else:
   t=X.find(y,s)+1
   if t:z+=[t]
 print(len(z))

Python: def calc_lcs(X, Y):
    max_lcs = 0
    m = len(X)
    n = len(Y)
    X = ' ' + X
    Y = ' ' + Y
    c = [[0]*1001 for i in range(1000+1)]
    for i in range(1, m+1):
        for j in range(1, n+1):
            if X[i] == Y[j]:
                c[i][j] = c[i - 1][j - 1] + 1
            elif c[i - 1][j] >= c[i][j - 1]:
                c[i][j] = c[i - 1][j]
            else:
                c[i][j] = c[i][j - 1]
            max_lcs = max(max_lcs, c[i][j])
    return max_lcs


if __name__ == '__main__':
    # ??????????????\???
    num = int(input())

    for _ in range(num):
        X = input()
        Y = input()
        # X = 'abcbdab'
        # Y = 'bdcaba'


        # ???????????????
        result = calc_lcs(X, Y)

        # ???????????¨???
        print(result)

Python: import sys

def lcs(X, Y):
    c = [0 for _ in range(len(Y) + 1)]
    for i in X:
        tmp = c[:]
        for ji, yc in enumerate(Y):
            j = ji + 1
            if i == yc:
                c[j] = tmp[j - 1] + 1
            elif c[j] < c[j - 1]:
                c[j] = c[j - 1]
    return c[-1]

n = int(input())

for i in range(n):
    X = sys.stdin.readline()[:-1]
    Y = sys.stdin.readline()[:-1]
    print(lcs(X, Y))

Python: from collections import defaultdict
q = int(input())
for _ in range(q):
    x = input()
    y = input()
    len_x = len(x)
    len_y = len(y)
    if len_x < len_y:
        len_x, len_y = len_y, len_x
        x, y = y, x
    c = defaultdict(list)
    for i, s in enumerate(x):
        c[s].append(i)
    li = [0] * len_x
    for s in y:
        if s in x:
            for i in c[s][::-1]:
                if i == 0:
                    li[i] = 1
                else:
                    li[i] = max(li[:i]) + 1
    print(max(li))

Python: # coding: utf-8

def array2d(d1, d2, init = None):
    return [[init for _ in range(d2)] for _ in range(d1)]


def solve():
    x = input().strip()
    y = input().strip()

    # dp[i][j]: x[:i], y[:j] ???LCS
    # dp[i][j] = max(dp[i-1][j], dp[i][j-1], dp[i-1][j-1]+1(if x[i]==y[j]))
    dp = array2d(len(x), len(y), 0)
    for i in range(len(x)):
        for j in range(len(y)):
            if i == 0 and j == 0:
                dp[0][0] = int(x[0] == y[0])
                continue
            if i > 0:
                dp[i][j] = max(dp[i][j], dp[i-1][j])
            if j > 0:
                dp[i][j] = max(dp[i][j], dp[i][j-1])
            if i > 0 and j > 0:
                cand = dp[i-1][j-1]
            else:
                cand = 0
            dp[i][j] = max(dp[i][j], cand + (x[i] == y[j]))
    return dp[-1][-1]


def main():
    cases = int(input())
    for i in range(cases):
        print(solve())

main()

Python: import bisect
import collections
import heapq
import itertools
import operator
import sys

dp = [[0] * 1010 for _ in range(1010)]

def lcs(x, y):
    for i, c in enumerate(y):
        if c == x[0]:
            dp[0][i] = 1
    for i, c in enumerate(x):
        if c == y[0]:
            dp[i][0] = 1
    for i in range(len(x)):
        for j in range(len(y)):
            if x[i] == y[j]:
                dp[i][j] = dp[i-1][j-1] + 1
            else:
                dp[i][j] = max(dp[i][j-1], dp[i-1][j])
    return dp[len(x)-1][len(y)-1]

def main():
    n = int(sys.stdin.readline())
    for _ in range(n):
        x = sys.stdin.readline().strip()
        y = sys.stdin.readline().strip()
        print(lcs(x, y))


if __name__ == '__main__':
    main()