LeetCode 422. Valid Word Square 验证单词平方

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.

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.

思路
1. 判断word[i][j]==word[j][i],注意对word[j][i]加保护，防止超出边界！！

class Solution {public:    bool validWordSquare(vector<string>& words) {        for(int i=0;i<words.size(）;i++){            for(int j=i+1；j<words[i].size(）;j++){                if(j>=words.size()||i>=words[j].size()||words[i][j]!=word[j][i]) //注意前面的两个边界条件是为了保证word[j][i]的存在，即：加保护！！                    return false;            }        }        return true;    }    };