Valid Word Square

https://leetcode.com/problems/valid-word-square/description/

Given a sequence of words, check whether it forms a valid word square.

A sequence of words forms a valid word square if the kth row and column read the exact same string, where 0 ≤ k < max(numRows, numColumns).

Note:

The number of words given is at least 1 and does not exceed 500.

Word length will be at least 1 and does not exceed 500.

Each word contains only lowercase English alphabet a-z.

Example 1:

Input:

[

"abcd",

"bnrt",

"crmy",

"dtye"

]

Output:

true

Explanation:

The first row and first column both read "abcd".

The second row and second column both read "bnrt".

The third row and third column both read "crmy".

The fourth row and fourth column both read "dtye".

Therefore, it is a valid word square.

Thoughts

第i行第j个元素要和第i列第j个元素相同, 不满足的情况为i >= 列上限, j >= 行上限或相应元素不相同.

Code

 class Solution {
     public boolean validWordSquare(List<String> words) {
         for (int i = 0; i < words.size(); i++) {
             for (int j = 0; j < words.get(i).length(); j++) {
                 if (j == words.size() || words.get(j).length() <= i || words.get(i).charAt(j) != words.get(j).charAt(i)) {
                     return false;
                 }
             }
         }

         return true;
     }
 }

Analysis

时间复杂度O(MN).