Submission #8314263

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Source Code Expand

from itertools import accumulate

n = int(input())
b = []
# iがあるインデックス
bc = {}
wc = {}
for i in range(2*n):
    c,a = input().split()
    a = int(a)
    b.append((c,a))
    if c == "B":
        bc[a]=i
    else:
        wc[a]=i

# black[i][j] : 黒のi(1-indexed)のある位置より左にある、i未満の個数 + 白のj以下の個数
black = [[0]*(n+1) for i in range(n+1)]
white = [[0]*(n+1) for i in range(n+1)]

for i in range(2*n):
    c,a = b[i]
    # 同色でa未満の個数 cnt
    cnt = 0
    num = [0]*(n+1)
    for j in range(i):
        if b[j][0] == c:
            if b[j][1] < a:
                cnt += 1
        else:
            num[b[j][1]] += 1
    # 累積和
    num = list(accumulate(num))
    if c == "B":
        black[a] = [j+cnt for j in num]
    else:
        white[a] = [j+cnt for j in num]

DP = [[float("inf")]*(n+1) for i in range(n+1)]
DP[0][0] = 0
for i in range(n+1):
    for j in range(n+1):
        # 黒がi個、白がj個→i+1, j or i, j+1
        if i+1 <= n:
            DP[i+1][j] = min(DP[i+1][j], DP[i][j]+bc[i+1]-black[i+1][j])
        if j+1 <= n:
            DP[i][j+1] = min(DP[i][j+1], DP[i][j]+wc[j+1]-white[j+1][i])
print(DP[n][n])

Submission Info

Judge Result