422. Valid Word Square π
Description
Given an array of strings words
, return true
if it forms a valid word square.
A sequence of strings forms a valid word square if the kth
row and column read the same string, where 0 <= k < max(numRows, numColumns)
.
Example 1:
Input: words = ["abcd","bnrt","crmy","dtye"] Output: true Explanation: The 1st row and 1st column both read "abcd". The 2nd row and 2nd column both read "bnrt". The 3rd row and 3rd column both read "crmy". The 4th row and 4th column both read "dtye". Therefore, it is a valid word square.
Example 2:
Input: words = ["abcd","bnrt","crm","dt"] Output: true Explanation: The 1st row and 1st column both read "abcd". The 2nd row and 2nd column both read "bnrt". The 3rd row and 3rd column both read "crm". The 4th row and 4th column both read "dt". Therefore, it is a valid word square.
Example 3:
Input: words = ["ball","area","read","lady"] Output: false Explanation: The 3rd row reads "read" while the 3rd column reads "lead". Therefore, it is NOT a valid word square.
Constraints:
1 <= words.length <= 500
1 <= words[i].length <= 500
words[i]
consists of only lowercase English letters.
Solutions
Solution 1: Iterative Check
We observe that if $words[i][j] \neq words[j][i]$, we can directly return false
.
Therefore, we only need to iterate through each row, and then check whether each row satisfies $words[i][j] = words[j][i]$. Note that if the index is out of bounds, we also directly return false
.
The time complexity is $O(n^2)$, where $n$ is the length of words
. The space complexity is $O(1)`.
1 2 3 4 5 6 7 8 |
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 |
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 |
|
1 2 3 4 5 6 7 8 9 10 11 |
|
1 2 3 4 5 6 7 8 9 10 11 12 |
|