LeetCode in Kotlin
3128. Right Triangles
Medium
You are given a 2D boolean matrix grid.
Return an integer that is the number of right triangles that can be made with the 3 elements of grid such that all of them have a value of 1.
Note:
- A collection of 3 elements of
gridis a right triangle if one of its elements is in the same row with another element and in the same column with the third element. The 3 elements do not have to be next to each other.
Example 1:
0 1 0
0 1 1
0 1 0
0 1 0
0 1 1
0 1 0
Input: grid = [[0,1,0],[0,1,1],[0,1,0]]
Output: 2
Explanation:
There are two right triangles.
Example 2:
1 0 0 0
0 1 0 1
1 0 0 0
Input: grid = [[1,0,0,0],[0,1,0,1],[1,0,0,0]]
Output: 0
Explanation:
There are no right triangles.
Example 3:
1 0 1
1 0 0
1 0 0
1 0 1
1 0 0
1 0 0
Input: grid = [[1,0,1],[1,0,0],[1,0,0]]
**Output: **2
Explanation:
There are two right triangles.
Constraints:
1 <= grid.length <= 10001 <= grid[i].length <= 10000 <= grid[i][j] <= 1
Solution
class Solution {
fun numberOfRightTriangles(grid: Array<IntArray>): Long {
val n = grid.size
val m = grid[0].size
val columns = IntArray(n)
val rows = IntArray(m)
var sum: Long = 0
for (i in 0 until n) {
for (j in 0 until m) {
columns[i] += grid[i][j]
rows[j] += grid[i][j]
}
}
for (i in 0 until n) {
for (j in 0 until m) {
sum += grid[i][j].toLong() * (rows[j] - 1) * (columns[i] - 1)
}
}
return sum
}
}