int 值 = X[i][j];

// JS code for above approach
let arr = [[1, 2, 3, 4],
		[5, 6, 7, 8],
		[9, 10, 11, 12]];
for (let i = 0; i < 3; i++) {
let s="";
	for (let j = 0; j < 4; j++) {
		s+=(arr[i][j]+" ");
	}
	console.log(s);
}

1 2 3 4 
5 6 7 8 
9 10 11 12 

<script>
	// JavaScript code for the above approach
	function searchInMatrix(arr, x) {
		let m = arr.length, n = arr[0].length;
		for (let i = 0; i < m; i++) {
			for (let j = 0; j < n; j++) {
				if (arr[i][j] == x)
					return true;
			}
		}
		return false;
	}

	// Driver program to test above

	let x = 8;
	let arr = [
    [0, 6, 8, 9, 11],
		[20, 22, 28, 29, 31],
		[36, 38, 50, 61, 63],
		[64, 66, 100, 122, 128]
  ];

	if (searchInMatrix(arr, x))
		document.write("YES" + "<br>");
	else
		document.write("NO" + "<br>");

</script>

# Python3 Program to print the Diagonals of a Matrix
MAX = 100

# Function to print the Principal Diagonal
def printPrincipalDiagonal(mat, n):
	print("Principal Diagonal: ",end="")

	for i in range(0,n):
		for j in range(0,n):

			# Condition for principal diagonal
			if (i == j):
				print(mat[i][j] , ", ", end="")
	print("")

# Function to print the Secondary Diagonal
def printSecondaryDiagonal(mat, n):
	print("Secondary Diagonal: ",end = "")

	for i in range(0,n):
		for j in range(0,n):

			# Condition for secondary diagonal
			if ((i + j) == (n - 1)):
				print(mat[i][j] , ", ", end = "")
	print("")

# Driver code
n = 4
a = [ [ 1, 2, 3, 4 ],
					[ 5, 6, 7, 8 ],
					[ 1, 2, 3, 4 ],
					[ 5, 6, 7, 8 ] ]

printPrincipalDiagonal(a, n)
printSecondaryDiagonal(a, n)

# This code is contributed by akashish__

主对角线：1, 6, 3, 8,
次对角线：4、7、2、5、

# Python Implementation to sort the given matrix
def sortMat(mat, n):
	
	# temporary matrix of size n^2
	temp = [0]*n*n
	k = 0
	
	# copy the elements of matrix one by one
	# leto temp[]
	for i in range(0, n):
		for j in range(0, n):
			temp[k] = mat[i][j]
			k += 1
	
	# sort temp[]
	temp.sort(reverse = True)
	
	# copy the elements of temp[] one by one
	# in mat[][]
	k = 0
	for i in range(0, n):
		for j in range(0, n):
			mat[i][j] = temp[k]
			k += 1
	
# function to print the given matrix
def printMat(mat, n):
	for i in range(0, n):
		for j in range(0, n):
			print(mat[i][j], end = ' ')
		print("")
	
# Driver program to test above
mat = [[5, 4, 7],
	[1, 3, 8],
	[2, 9, 6]]
n = 3
	
print("Original Matrix:")
printMat(mat, n)
sortMat(mat, n)
print("\nMatrix After Sorting:")
printMat(mat, n)

# This code is contributed by ishankhandelwals.

# Python program for left rotation of matrix by 180
R = 4
C = 4

# Function to rotate the matrix by 180 degree
def reverseColumns(arr):
for i in range(C):
	for j in range(0, int(C / 2)):
	x = arr[j][i]
	arr[j][i] = arr[C - 1 - j][i]
	arr[C - 1 - j][i] = x

# Function for transpose of matrix
def transpose(arr):
for i in range(R):
	for j in range(i, C):
	x = arr[j][i]
	arr[j][i] = arr[i][j]
	arr[i][j] = x

# Function for display the matrix
def printMatrix(arr):
for i in range(R):
	for j in range(C):
	print(arr[i][j], end = ' ')
	print()

# Function to anticlockwise rotate matrix
# by 180 degree
def rotate180(arr):
transpose(arr)
reverseColumns(arr)
transpose(arr)
reverseColumns(arr)

# Driven code
arr = [[1, 2, 3, 4 ],
			[ 5, 6, 7, 8 ],
			[ 9, 10, 11, 12 ],
			[ 13, 14, 15, 16 ]]
rotate180(arr)
printMatrix(arr)

# This code is contributed by akashish__

// Javascript program for left rotation of matrix by 180


let R= 4
let C= 4

// Function to rotate the matrix by 180 degree
function reverseColumns(arr)
{
	for (let i = 0; i < C; i++)
		for (let j = 0, k = C - 1; j < k; j++, k--)
			{
			let x= arr[j][i];
			arr[j][i] = arr[k][i];
			arr[k][i]=x;
			}
			
}

// Function for transpose of matrix
function transpose(arr)
{
	for (let i = 0; i < R; i++)
		for (let j = i; j < C; j++)
			{
			let x= arr[j][i];
			arr[j][i] = arr[i][j];
			arr[i][j]=x;
		}
}

// Function for display the matrix
function printMatrix(arr)
{
	document.write(arr);
}

// Function to anticlockwise rotate matrix
// by 180 degree
function rotate180(arr)
{
	transpose(arr);
	reverseColumns(arr);
	transpose(arr);
	reverseColumns(arr);
}

// Driven code

	let arr = [[1, 2, 3, 4 ],
					[ 5, 6, 7, 8 ],
					[ 9, 10, 11, 12 ],
					[ 13, 14, 15, 16 ]];
	rotate180(arr);
	printMatrix(arr);

# Python program to find unique
# element in matrix

# Function that calculate unique element
def unique(mat, n, m):
	maximum = 0
	flag = 0
	for i in range(n):
		for j in range(m):
			# Find maximum element in
			# a matrix
			if maximum < mat[i][j]:
				maximum = mat[i][j]

	# Take 1-D array of (maximum + 1)
	# size
	b = [0] * (maximum + 1)
	for i in range(n):
		for j in range(m):
			y = mat[i][j]
			b[y] += 1

	# print unique element
	for i in range(1, maximum+1):
		if b[i] == 1:
			print(i, end=' ')
	flag = 1

	if flag == 0:
		print("No unique element in the matrix")

R = 4
C = 4
mat = [[1, 2, 3, 20],
	[5, 6, 20, 25],
	[1, 3, 5, 6],
	[6, 7, 8, 15]]

# function that calculate unique element
unique(mat, R, C)

# This code is contributed by lokesh.

// JS code

let mat = [[1, 2, 3, 20], [5, 6, 20, 25], [1, 3, 5, 6], [6, 7, 8, 15]];

let max = 0;
let flag = 0;
for (let i = 0; i < mat.length; i++) {
for (let j = 0; j < mat.length; j++) {
	if (max < mat[i][j]) {
	max = mat[i][j];
	}
}
}

let b = new Array(max + 1).fill(0);
for (let i = 0; i < mat.length; i++) {
for (let j = 0; j < mat.length; j++) {
	let y = mat[i][j];
	b[y]++;
}
}

for (let i = 1; i <= max; i++) {
if (b[i] == 1) {
	console.log(i + " ");
	flag = 1;
}
}

if (!flag) {
console.log("No unique element in the matrix");
}