LeetCode in Kotlin
1277. Count Square Submatrices with All Ones
Medium
Given a m * n matrix of ones and zeros, return how many square submatrices have all ones.
Example 1:
Input: matrix = [ [0,1,1,1], [1,1,1,1], [0,1,1,1] ]
Output: 15
Explanation:
There are 10 squares of side 1.
There are 4 squares of side 2.
There is 1 square of side 3.
Total number of squares = 10 + 4 + 1 = 15.
Example 2:
Input: matrix = [ [1,0,1], [1,1,0], [1,1,0] ]
Output: 7
Explanation:
There are 6 squares of side 1.
There is 1 square of side 2.
Total number of squares = 6 + 1 = 7.
Constraints:
1 <= arr.length <= 3001 <= arr[0].length <= 3000 <= arr[i][j] <= 1
Solution
class Solution {
fun countSquares(matrix: Array<IntArray>): Int {
var total = 0
for (ints in matrix) {
total += ints[0]
}
for (i in 1 until matrix[0].size) {
total += matrix[0][i]
}
for (i in 1 until matrix.size) {
for (j in 1 until matrix[0].size) {
if (matrix[i][j] == 1) {
matrix[i][j] = (
Math.min(
matrix[i - 1][j - 1],
Math.min(matrix[i - 1][j], matrix[i][j - 1]),
) +
1
)
}
total += matrix[i][j]
}
}
return total
}
}