{ "data": { "question": { "questionId": "3235", "questionFrontendId": "2976", "boundTopicId": null, "title": "Minimum Cost to Convert String I", "titleSlug": "minimum-cost-to-convert-string-i", "content": "
You are given two 0-indexed strings source
and target
, both of length n
and consisting of lowercase English letters. You are also given two 0-indexed character arrays original
and changed
, and an integer array cost
, where cost[i]
represents the cost of changing the character original[i]
to the character changed[i]
.
You start with the string source
. In one operation, you can pick a character x
from the string and change it to the character y
at a cost of z
if there exists any index j
such that cost[j] == z
, original[j] == x
, and changed[j] == y
.
Return the minimum cost to convert the string source
to the string target
using any number of operations. If it is impossible to convert source
to target
, return -1
.
Note that there may exist indices i
, j
such that original[j] == original[i]
and changed[j] == changed[i]
.
\n
Example 1:
\n\n\nInput: source = "abcd", target = "acbe", original = ["a","b","c","c","e","d"], changed = ["b","c","b","e","b","e"], cost = [2,5,5,1,2,20]\nOutput: 28\nExplanation: To convert the string "abcd" to string "acbe":\n- Change value at index 1 from 'b' to 'c' at a cost of 5.\n- Change value at index 2 from 'c' to 'e' at a cost of 1.\n- Change value at index 2 from 'e' to 'b' at a cost of 2.\n- Change value at index 3 from 'd' to 'e' at a cost of 20.\nThe total cost incurred is 5 + 1 + 2 + 20 = 28.\nIt can be shown that this is the minimum possible cost.\n\n\n
Example 2:
\n\n\nInput: source = "aaaa", target = "bbbb", original = ["a","c"], changed = ["c","b"], cost = [1,2]\nOutput: 12\nExplanation: To change the character 'a' to 'b' change the character 'a' to 'c' at a cost of 1, followed by changing the character 'c' to 'b' at a cost of 2, for a total cost of 1 + 2 = 3. To change all occurrences of 'a' to 'b', a total cost of 3 * 4 = 12 is incurred.\n\n\n
Example 3:
\n\n\nInput: source = "abcd", target = "abce", original = ["a"], changed = ["e"], cost = [10000]\nOutput: -1\nExplanation: It is impossible to convert source to target because the value at index 3 cannot be changed from 'd' to 'e'.\n\n\n
\n
Constraints:
\n\n1 <= source.length == target.length <= 105
source
, target
consist of lowercase English letters.1 <= cost.length == original.length == changed.length <= 2000
original[i]
, changed[i]
are lowercase English letters.1 <= cost[i] <= 106
original[i] != changed[i]
(a, b)
with weight c
if we can change from character a
to letter b
with cost c
. (Keep the one with the smallest cost in case there are multiple edges between a
and b
).",
"Calculate the shortest path for each pair of characters (source[i], target[i])
. The sum of cost over all i
in the range [0, source.length - 1]
. If there is no path between source[i]
and target[i]
, the answer is -1
.",
"Any shortest path algorithms will work since we only have 26
nodes. Since we only have at most 26 * 26
pairs, we can save the result to avoid re-calculation.",
"We can also use Floyd Warshall's algorithm to precompute all the results."
],
"solution": null,
"status": null,
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