Buggy python submission (verdict: Time Limit Exceeded):
def main():
    S = input()
    T = input()
    dp = [[0] * (len(S) + 1) for _ in range(len(T) + 1)]
    for j, t in enumerate(T, 1):
        for i, s in enumerate(S, 1):
            dp[j][i] = max(dp[j - 1][i], dp[j][i - 1], dp[j - 1][i - 1] + 1 if s == t else 0)
    i, j = len(S), len(T)
    R = ''
    while i > 0 and j > 0:
        n = dp[j][i]
        if dp[j - 1][i] == n:
            j -= 1
        elif dp[j][i - 1] == n:
            i -= 1
        elif dp[j - 1][i - 1] == n - 1:
            j -= 1
            i -= 1
            R += T[j]
        else:
            assert False
    return R[::-1]

print(main())


Fixed submission:
def main():
    s = input()
    t = input()
    v = [0] * (len(t) + 1)
    dp = [v]
    for i, si in enumerate(s, 1):
        u, v = v, v.copy()
        dp.append(v)
        ll, ul = 0, 0
        for j, ti in enumerate(t, 1):
            uu = u[j]
            if si == ti:
                v[j] = ll = ul + 1
            else:
                if ll > uu:
                    v[j] = ll
                else:
                    ll = uu
            ul = uu
    k = dp[i][j]
    r = ''
    while k:
        if dp[i - 1][j] == k:
            i -= 1
        elif dp[i][j - 1] == k:
            j -= 1
        else:
            k -= 1
            i -= 1
            j -= 1
            r += s[i]
    print(r[::-1])

main()

Buggy python submission (verdict: Time Limit Exceeded):
def main():
    s, t = input(), input()
    dp = ['' for _ in range(len(t) + 1)]
    for i, si in enumerate(s, 1):
        u = ''
        for j, ti in enumerate(t, 1):
            d = u
            l = dp[j - 1]
            u = dp[j]
            if si == ti:
                dp[j] = d + si
            else:
                if len(l) > len(u):
                    dp[j] = l
    print(dp[-1])


main()


Fixed submission:
def main():
    s = input()
    t = input()
    v = [0] * (len(t) + 1)
    dp = [v]
    for i, si in enumerate(s, 1):
        u, v = v, v.copy()
        dp.append(v)
        ll, ul = 0, 0
        for j, ti in enumerate(t, 1):
            uu = u[j]
            if si == ti:
                v[j] = ll = ul + 1
            else:
                if ll > uu:
                    v[j] = ll
                else:
                    ll = uu
            ul = uu
    k = dp[i][j]
    r = ''
    while k:
        if dp[i - 1][j] == k:
            i -= 1
        elif dp[i][j - 1] == k:
            j -= 1
        else:
            k -= 1
            i -= 1
            j -= 1
            r += s[i]
    print(r[::-1])

main()

Buggy python submission (verdict: Time Limit Exceeded):
def main():
    s, t = input(), input()
    v = [('', False) for _ in range(len(t) + 1)]
    w = [('', False) for _ in range(len(t) + 1)]
    for i in range(1, len(s) + 1):
        for j in range(1, len(t) + 1):
            u, uu = v[j]
            l, ll = w[j - 1]
            d, dd = v[j - 1]
            if s[i - 1] == t[j - 1]:
                if len(u) > len(l) and not uu:
                    l, ll = u, uu 
                if len(l) > len(d) and not ll:
                    d, dd = l, ll
                w[j] = (d + s[i - 1], True)
            else:
                if len(u) > len(l):
                    l, ll = u, uu
                dd = False
                if len(l) > len(d):
                    d, dd = l, ll
                w[j] = (d, dd)
        v, w = w, v
    print(v[-1][0])


main()


Fixed submission:
def main():
    s = input()
    t = input()
    v = [0] * (len(t) + 1)
    dp = [v]
    for i, si in enumerate(s, 1):
        u, v = v, v.copy()
        dp.append(v)
        ll, ul = 0, 0
        for j, ti in enumerate(t, 1):
            uu = u[j]
            if si == ti:
                v[j] = ll = ul + 1
            else:
                if ll > uu:
                    v[j] = ll
                else:
                    ll = uu
            ul = uu
    k = dp[i][j]
    r = ''
    while k:
        if dp[i - 1][j] == k:
            i -= 1
        elif dp[i][j - 1] == k:
            j -= 1
        else:
            k -= 1
            i -= 1
            j -= 1
            r += s[i]
    print(r[::-1])

main()

Buggy python submission (verdict: Time Limit Exceeded):
def main():
    s, t = input(), input()
    v = [('', False) for i in range(len(t) + 1)]
    for i in range(1, len(s) + 1):
        w = [('', False) for _ in range(len(t) + 1)]
        for j in range(1, len(t) + 1):
            u, uu = v[j]
            l, ll = w[j - 1]
            d, dd = v[j - 1]
            if s[i - 1] == t[j - 1]:
                if len(u) > len(l) and not uu:
                    l, ll = u, uu 
                if len(l) > len(d) and not ll:
                    d, dd = l, ll
                w[j] = (d + s[i - 1], True)
            else:
                if len(u) > len(l):
                    l, ll = u, uu
                dd = False
                if len(l) > len(d):
                    d, dd = l, ll
                w[j] = (d, dd)
        v = w
    print(v[-1][0])


main()


Fixed submission:
def main():
    s = input()
    t = input()
    v = [0] * (len(t) + 1)
    dp = [v]
    for i, si in enumerate(s, 1):
        u, v = v, v.copy()
        dp.append(v)
        ll, ul = 0, 0
        for j, ti in enumerate(t, 1):
            uu = u[j]
            if si == ti:
                v[j] = ll = ul + 1
            else:
                if ll > uu:
                    v[j] = ll
                else:
                    ll = uu
            ul = uu
    k = dp[i][j]
    r = ''
    while k:
        if dp[i - 1][j] == k:
            i -= 1
        elif dp[i][j - 1] == k:
            j -= 1
        else:
            k -= 1
            i -= 1
            j -= 1
            r += s[i]
    print(r[::-1])

main()