solves special position in inary matrix

Author: anishLearnsToCode

README.md

@@ -395,3 +395,4 @@
 | 1566 | [Detect Pattern of Length M Repeated K or More Times](https://leetcode.com/problems/detect-pattern-of-length-m-repeated-k-or-more-times)             |                                                   [![Java](assets/java.png)](src/DetectPatternOfLengthMRepeatedKOrMoreTimes.java)                                                    |                                                                                                                                   |
 | 1572 | [Matrix Diagonal Sum](https://leetcode.com/problems/matrix-diagonal-sum)                                                                             |                                                                [![Java](assets/java.png)](src/MatrixDiagonalSum.java)                                                                |                                                                                                                                   |
 | 1576 | [Replace All ?'s to Avoid Consecutive Repeating Characters](https://leetcode.com/problems/replace-all-s-to-avoid-consecutive-repeating-characters)   |                                                 [![Java](assets/java.png)](src/ReplaceAllToAvoidConsecutiveRepeatingCharacters.java)                                                 |                                                                                                                                   |
+| 1582 | [Special Positions in a Binary Matrix](https://leetcode.com/problems/special-positions-in-a-binary-matrix)                                           |                                                 [![Java](assets/java.png)](src/SpecialPositionInABinaryMatrix.java)                                                 |                                                                                                                                   |

src/SpecialPositionInABinaryMatrix.java

@@ -0,0 +1,51 @@
+// https://leetcode.com/problems/special-positions-in-a-binary-matrix
+// T: O(n * m)
+// S: O(n + m)
+
+import java.util.Arrays;
+
+public class SpecialPositionInABinaryMatrix {
+    public int numSpecial(int[][] matrix) {
+        final int[] rowSum = getRowSum(matrix);
+        final ColumnSumData columnSumData = getColumnSum(matrix);
+        final int[] columnSumOneRowIndex = columnSumData.oneIndex;
+        final int[] columnSum = columnSumData.sum;
+        int specialPositions = 0;
+        for (int i = 0 ; i < columnSum.length ; i++) {
+            if (columnSum[i] == 1 && rowSum[columnSumOneRowIndex[i]] == 1) {
+                specialPositions++;
+            }
+        }
+        return specialPositions;
+    }
+
+    private int[] getRowSum(int[][] matrix) {
+        final int[] sum = new int[matrix.length];
+        for (int i = 0 ; i < sum.length ; i++) {
+            sum[i] = Arrays.stream(matrix[i]).sum();
+        }
+        return sum;
+    }
+
+    private ColumnSumData getColumnSum(int[][] matrix) {
+        final int[] sum = new int[matrix[0].length];
+        final int[] indexes = new int[sum.length];
+        for (int i = 0 ; i < sum.length ; i++) {
+            for (int row = 0 , index = 0 ; row < matrix.length ; row++) {
+                sum[i] += matrix[row][i];
+                if (matrix[row][i] == 1) indexes[i] = row;
+            }
+        }
+        return new ColumnSumData(sum, indexes);
+    }
+
+    private static final class ColumnSumData {
+        private final int[] sum;
+        private final int[] oneIndex;
+
+        private ColumnSumData(int[] sum, int[] oneIndex) {
+            this.sum = sum;
+            this.oneIndex = oneIndex;
+        }
+    }
+}