Problem solution 1277 “Count Square Submatrices with All Oness” from LeetCode.
Problem
Given a m * n matrix of ones and zeros, return how many square submatrices have all ones.
Constraints:
- 1 <=
len(arr) <= 300
- 1 <=
len(arr[0]) <= 300
- 0 <=
arr[i][j] <= 1
example
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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.
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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.
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Solution
DFS
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func countSquares(matrix [][]int) int {
sum:=0
for i:=range matrix {
for j:=range matrix[i] {
sum+=helper(matrix, i, j, 0)
}
}
return sum
}
func helper(m [][]int, i,j,l int) int {
if i>=len(m) || j>=len(m[0] ) {
return 0
}
if m[i][j] == 0 {
return 0
}
sum := 0
f := true
for idx:=1; idx<=l;idx++ {
f = f && i-idx>=0 && j-idx>=0 &&m[i-idx][j] == 1 &&m[i][j-idx] == 1
}
if f {
sum++
sum += helper(m,i+1,j+1,l+1)
}
return sum
}
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