766. Toeplitz Matrix

#### QUESTION:

A matrix is Toeplitz if every diagonal from top-left to bottom-right has the same element.

Now given an `M x N` matrix, return `True` if and only if the matrix is Toeplitz.

Example 1:

``````Input: matrix = [[1,2,3,4],[5,1,2,3],[9,5,1,2]]
Output: True
Explanation:
1234
5123
9512

In the above grid, the diagonals are "[9]", "[5, 5]", "[1, 1, 1]", "[2, 2, 2]", "[3, 3]", "[4]", and in each diagonal all elements are the same, so the answer is True.

``````

Example 2:

``````Input: matrix = [[1,2],[2,2]]
Output: False
Explanation:
The diagonal "[1, 2]" has different elements.

``````

Note:

1. `matrix` will be a 2D array of integers.
2. `matrix` will have a number of rows and columns in range `[1, 20]`.
3. `matrix[i][j]` will be integers in range `[0, 99]`.

#### EXPLANATION:

1.首先处理横向的情况：横向的时候就进行遍历操作，对j进行遍历，然后进行判断，这样就可以了。

2.进行竖向操作的时候，只需要进行一次斜的遍历，这样就可以避免重复操作了。

x,x,x,x,x,x

o,x,x,x,x,x

o,o,x,x,x,x

o,o,o,x,x,x

o,o,o,o,x,x

o,o,o,o,o,x

x,x,x,x,x,x

x,x,x,x,x,x

o,x,x,x,x,x

o,o,x,x,x,x

o,o,o,x,x,x

o,o,o,o,x,x

x,x,x,x,x,x

x,x,x,x,x,x

x,x,x,x,x,x

o,x,x,x,x,x

o,o,x,x,x,x

o,o,o,x,x,x

#### SOLUTION:

``````class Solution {
public boolean isToeplitzMatrix(int[][] matrix) {
for(int i = 0;i<matrix.length;i++){
if(i==0){
for(int j = 0;j<matrix[i].length;j++){
int m = 0;int n=j;
int tmp = matrix[m][n];
while (m<matrix.length&&n<matrix[m].length){
if(matrix[m][n]!=tmp) return false;
m++;n++;
}
}
}else{
int m = i;int n=0;
int tmp = matrix[m][n];
while (m<matrix.length&&n<matrix[m].length){
if(matrix[m][n]!=tmp) return false;
m++;n++;
}
}
}
return true;
}
}
``````
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