2026-01-30 17:30:09 +0000 UTC
Minimum Cost to Convert String II
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Code
INF = 10**18
INF_INT = 10**9
class Solution:
def minimumCost(
self,
source: str,
target: str,
original: List[str],
changed: List[str],
cost: List[int],
) -> int:
n = len(source)
m = len(original)
child = [[-1] * 26]
tid = [-1]
def new_node() -> int:
child.append([-1] * 26)
tid.append(-1)
return len(child) - 1
idx = -1
def add(word: str) -> int:
nonlocal idx
node = 0
for ch in word:
c = ord(ch) - 97
nxt = child[node][c]
if nxt == -1:
nxt = new_node()
child[node][c] = nxt
node = nxt
if tid[node] == -1:
idx += 1
tid[node] = idx
return tid[node]
edges = []
for i in range(m):
x = add(original[i])
y = add(changed[i])
edges.append((x, y, cost[i]))
P = idx + 1
if P == 0:
return 0 if source == target else -1
dist = [[INF_INT] * P for _ in range(P)]
for i in range(P):
dist[i][i] = 0
for x, y, w in edges:
if w < dist[x][y]:
dist[x][y] = w
for k in range(P):
dk = dist[k]
for i in range(P):
di = dist[i]
dik = di[k]
if dik == INF_INT:
continue
base = dik
for j in range(P):
nd = base + dk[j]
if nd < di[j]:
di[j] = nd
dp = [INF] * (n + 1)
dp[0] = 0
s_arr = [ord(c) - 97 for c in source]
t_arr = [ord(c) - 97 for c in target]
for j in range(n):
if dp[j] >= INF:
continue
base = dp[j]
if source[j] == target[j] and base < dp[j + 1]:
dp[j + 1] = base
u = 0
v = 0
for i in range(j, n):
u = child[u][s_arr[i]]
v = child[v][t_arr[i]]
if u == -1 or v == -1:
break
uid = tid[u]
vid = tid[v]
if uid != -1 and vid != -1:
w = dist[uid][vid]
if w != INF_INT:
ni = i + 1
cand = base + w
if cand < dp[ni]:
dp[ni] = cand
ans = dp[n]
return -1 if ans >= INF else ans