- Difficulty: Easy
- Tags: LeetCode, Easy, Array, Math, Matrix, Number Theory, leetcode-2614, O(MAXN), Linear Sieve of Eratosthenes
Problem
You are given a 0-indexed two-dimensional integer array nums
.
Return the largest prime number that lies on at least one of the diagonals of nums
. In case, no prime is present on any of the diagonals, return 0.
Note that:
- An integer is prime if it is greater than
1
and has no positive integer divisors other than1
and itself. - An integer
val
is on one of the diagonals ofnums
if there exists an integeri
for whichnums[i][i] = val
or ani
for whichnums[i][nums.length - i - 1] = val
.
In the above diagram, one diagonal is [1,5,9] and another diagonal is [3,5,7].
Example 1:
Input: nums = [[1,2,3],[5,6,7],[9,10,11]] Output: 11 Explanation: The numbers 1, 3, 6, 9, and 11 are the only numbers present on at least one of the diagonals. Since 11 is the largest prime, we return 11.
Example 2:
Input: nums = [[1,2,3],[5,17,7],[9,11,10]] Output: 17 Explanation: The numbers 1, 3, 9, 10, and 17 are all present on at least one of the diagonals. 17 is the largest prime, so we return 17.
Constraints:
1 <= nums.length <= 300
nums.length == numsi.length
1 <= nums[i][j] <= 4*106