Buggy python submission (verdict: Time Limit Exceeded):
def main():
  s = input()
  t = input()
  sn, tn = len(s), len(t)
  dp = [[0]*(tn+1) for _ in range(sn+1)]
  for i, si in enumerate(s):
    di, di2 = dp[i], dp[i+1]
    for j, ti in enumerate(t):
      if si == ti:
        di2[j+1] = di[j] + 1
      else:
          if di[j+1] > di[j]:
              di2[j+1] = di[j+1]
          else:
              di2[j+1] = di2[j]
    dp[i+1] = di2
  ans = ""
  while sn and tn:
    di = dp[sn][tn]
    if di == dp[sn][tn-1]:
      tn -= 1
    elif di == dp[sn-1][tn]:
      sn -= 1
    else:
      tn -= 1
      sn -= 1
      ans += s[sn]
      
  print(ans[::-1])

if __name__ == "__main__":
  main()

Fixed submission:
def main():
  s = input()
  t = input()
  sn, tn = len(s), len(t)
  dp = [[0]*(tn+1) for _ in range(sn+1)]
  for i, si in enumerate(s):
    di, di2 = dp[i], dp[i+1]
    for j, ti in enumerate(t):
      if si == ti:
        di2[j+1] = di[j] + 1
      else:
          if di[j+1] > di[j]:
              di2[j+1] = di[j+1]
          else:
              di2[j+1] = di2[j]
    dp[i+1] = di2
  ans = ""
  while sn and tn:
    di = dp[sn][tn]
    if di == dp[sn][tn-1]:
      tn -= 1
    elif di == dp[sn-1][tn]:
      sn -= 1
    else:
      tn -= 1
      sn -= 1
      ans += s[sn]
      
  print(ans[::-1])

if __name__ == "__main__":
  main()

Buggy python submission (verdict: Time Limit Exceeded):
def main():
  s = input()
  t = input()
  sn, tn = len(s), len(t)
  dp = [[""]*(tn+1) for _ in range(sn+1)]
  for i, si in enumerate(s):
    di, di2 = dp[i], dp[i+1]
    for j, ti in enumerate(t):
      ji = j+1
      if si == ti:
        di2[ji] = di[j] + si
      else:
          if len(di[ji]) > len(di2[j]):
              di2[ji] = di[ji]
          else:
              di2[ji] = di2[j]
    dp[i+1] = di2
  print(dp[sn][tn])

if __name__ == "__main__":
  main()

Fixed submission:
def main():
  s = input()
  t = input()
  sn, tn = len(s), len(t)
  dp = [[0]*(tn+1) for _ in range(sn+1)]
  for i, si in enumerate(s):
    di, di2 = dp[i], dp[i+1]
    for j, ti in enumerate(t):
      if si == ti:
        di2[j+1] = di[j] + 1
      else:
          if di[j+1] > di[j]:
              di2[j+1] = di[j+1]
          else:
              di2[j+1] = di2[j]
    dp[i+1] = di2
  ans = ""
  while sn and tn:
    di = dp[sn][tn]
    if di == dp[sn][tn-1]:
      tn -= 1
    elif di == dp[sn-1][tn]:
      sn -= 1
    else:
      tn -= 1
      sn -= 1
      ans += s[sn]
      
  print(ans[::-1])

if __name__ == "__main__":
  main()

Buggy python submission (verdict: Time Limit Exceeded):
def main():
  s = input()
  t = input()
  sn, tn = len(s), len(t)
  dp = [[""]*(tn+1) for _ in range(sn+1)]
  for i, si in enumerate(s):
    di, di2 = dp[i], dp[i+1]
    for j, ti in enumerate(t):
      if si == ti:
        di2[j+1] = di[j] + si
      else:
          if len(di[j+1]) > len(di[j]):
              di2[j+1] = di[j+1]
          else:
              di2[j+1] = di2[j]
    dp[i+1] = di2
  print(dp[sn][tn])

if __name__ == "__main__":
  main()

Fixed submission:
def main():
  s = input()
  t = input()
  sn, tn = len(s), len(t)
  dp = [[0]*(tn+1) for _ in range(sn+1)]
  for i, si in enumerate(s):
    di, di2 = dp[i], dp[i+1]
    for j, ti in enumerate(t):
      if si == ti:
        di2[j+1] = di[j] + 1
      else:
          if di[j+1] > di[j]:
              di2[j+1] = di[j+1]
          else:
              di2[j+1] = di2[j]
    dp[i+1] = di2
  ans = ""
  while sn and tn:
    di = dp[sn][tn]
    if di == dp[sn][tn-1]:
      tn -= 1
    elif di == dp[sn-1][tn]:
      sn -= 1
    else:
      tn -= 1
      sn -= 1
      ans += s[sn]
      
  print(ans[::-1])

if __name__ == "__main__":
  main()