Ruudukko

a = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'

char = {'A': 0, 'B': 1, 'C': 2, 'D': 3, 'E': 4, 'F': 5, 'G': 6, 'H': 7, 'I': 8, 'J': 9, 'K': 10, 'L': 11, 'M': 12, 'N': 13, 'O': 14, 'P': 15, 'Q': 16, 'R': 17, 'S': 18, 'T': 19, 'U': 20, 'V': 21, 'W': 22, 'X': 23, 'Y': 24, 'Z': 25}

n = int(input())

r = [[e for e in input()] for i in range(n)]


answer = ['*'] * (2*n-1)
answer[0] = r[0][0]



def forward(i, j, p):
    global answer
    if i+j+p == 2*n-2:
        answer[i+j+p] = r[n-1][n-1]
        return

    memory = [26, 0, 0, '*']
    count = 0
    for k in range(p+1):
        i1 = i + k
        j1 = j + p - k
        if j1 > n-1:
            continue
        if i1 > n-1:
            break
        if char[r[i1][j1]] < memory[0]:
            memory = [char[r[i1][j1]], i1, j1, r[i1][j1]]
            count += 1

    answer[i+j+p] = memory[3] #23
    if count > 1:
        f(memory[1], memory[2])
        return
    else:
        forward(i, j, p+1)



def f(i, j):
    global answer
    
    if i + j + 1 == 2*n-2:
        answer[i+j+1] = r[n-1][n-1]
        return
    if i == n-1:
        answer[i+j+1] = r[i][j+1]
        f(i, j+1)
    elif j == n-1:
        answer[i+j+1] = r[i+1][j]
        f(i+1, j)
    
    else:
        if char[r[i][j+1]] < char[r[i+1][j]]:
            answer[i+j+1] = r[i][j+1] #24, 26
            f(i, j+1)
        elif char[r[i+1][j]] < char[r[i][j+1]]:
            answer[i+j+1] = r[i+1][j]
            f(i+1, j)
        else:
            answer[i+j+1] = r[i][j+1]
            forward(i, j, 2)
        

if n > 1:
    f(0, 0)


print(''.join(answer))

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: WRONG ANSWER

Test 9

Group: 2

Verdict: WRONG ANSWER

Test 10

Group: 2

Verdict: WRONG ANSWER

Test 11

Group: 3

Verdict: ACCEPTED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: WRONG ANSWER

Test 14

Group: 3

Verdict: WRONG ANSWER

Test 15

Group: 3

Verdict: WRONG ANSWER