# 2133. Check if Every Row and Column Contains All Numbers

##

## use set to check row, then col

```java
class Solution {
    public boolean checkValid(int[][] matrix) {
        int n = matrix.length;

        Set<Integer> set = new HashSet<>();
        for (int i = 0 ; i < n; i++) {
            for (int j = 0 ; j < n; j++) {
                // if there is a number existed, it's wrong!
                if (set.contains(matrix[i][j])) {
                    return false;
                }
                set.add(matrix[i][j]);
            }
            set = new HashSet<>();
        }
        
        set = new HashSet<>();
        for (int j = 0 ; j < n; j++) {
            for (int i = 0 ; i < n; i++) {
                // if there is a number existed, it's wrong!
                if (set.contains(matrix[i][j])) {
                    return false;
                }
                set.add(matrix[i][j]);
            }
            set = new HashSet<>();
        }
        return true;
    }
}
```

## use Xor

![](https://4272748102-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LekNH5IywF8mjBxFcnu%2Fuploads%2FqIv9uVLsd09XVpb3CL0S%2Fimage.png?alt=media\&token=c7f03f0b-bc8b-4b31-bbd1-52d256e217ae)

T: O(n^2)

S: O(1)

```java
class Solution {
    public boolean checkValid(int[][] matrix) {
        int n = matrix.length;
        
        for (int i = 0 ; i < n; i++) {
            int rowXor = 0; // 逐 row 檢查
            int colXor = 0; // 逐 col 檢查
            for (int j = 0 ; j < n; j++) {
                rowXor ^= matrix[i][j]^(j+1);
                colXor ^= matrix[j][i]^(j+1);
            }
            if (rowXor != 0 || colXor != 0) {
                return false;
            }
        }
        
        
        return true;
    }
}
```


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