422. Valid Word Square

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Problem

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:
[
  "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.

Example 2:

Input:
[
  "abcd",
  "bnrt",
  "crm",
  "dt"
]

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 "crm".
The fourth row and fourth column both read "dt".

Therefore, it is a valid word square.

Example 3:

Input:
[
  "ball",
  "area",
  "read",
  "lady"
]

Output:
false

Explanation:
The third row reads "read" while the third column reads "lead".

Therefore, it is NOT a valid word square.

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() || i >= words.get(j).length()) return false;
                
                char c1 = words.get(i).charAt(j);
                char c2 = words.get(j).charAt(i);
                if(c1 != c2) return false;
            }
        }
        
        return true;
    }
}