1582. Special Positions in a Binary Matrix-二进制矩阵中的特殊位置

Given a rows x cols matrix mat, where mat[i][j] is either 0 or 1, return the number of special positions in mat.

A position (i,j) is called special if mat[i][j] == 1 and all other elements in row i and column j are 0 (rows and columns are 0-indexed).

Example 1:
Input:
mat =
[[1,0,0],
  [0,0,1],
  [1,0,0]]
Output: 1
Explanation: (1,2) is a special position because mat[1][2] == 1 and all other elements in row 1 and column 2 are 0.

Example 2:
Input:
mat =
[[1,0,0],
  [0,1,0],
  [0,0,1]]
Output: 3
Explanation: (0,0), (1,1) and (2,2) are special positions.

Example 3:
Input:
mat =
[[0,0,0,1],
  [1,0,0,0],
  [0,1,1,0],
  [0,0,0,0]]
Output: 2

Example 4:
Input:
mat =
[[0,0,0,0,0],
  [1,0,0,0,0],
  [0,1,0,0,0],
  [0,0,1,0,0],
  [0,0,0,1,1]]
Output: 3

Constraints:

• rows == mat.length
• cols == mat[i].length
• 1 <= rows, cols <= 100
• mat[i][j] is 0 or 1.

Solution in python:

class Solution:
    def numSpecial(self, mat: List[List[int]]) -> int:
        temp = []
        count = 0
        for i in range(len(mat)):
            if sum(mat[i]) == 1:
                temp.append(i)
        for i in temp:
            for j in range(len(mat[0])):
                if mat[i][j] == 1:
                    flag = 1
                    for k in range(0, i):
                        if mat[k][j] != 0:
                            flag = 0
                            break
                    if flag:
                        for k in range(i+1, len(mat)):
                            if mat[k][j] != 0:
                                flag = 0
                                break
                    if flag:
                        count += 1
        return count