add: LargestSquareInAMatrixOptimized

Author: Jer3myYu

java/Dynamic Programming/LargestSquareInAMatrixOptimized.java

@@ -0,0 +1,32 @@
+public class LargestSquareInAMatrixOptimized {
+    public int largestSquareInAMatrixOptimized(int[][] matrix) {
+        if (matrix == null || matrix.length == 0 || matrix[0] == null || matrix[0].length == 0) {
+            return 0;
+        }
+        int m = matrix.length;
+        int n = matrix[0].length;
+        int[] prevRow = new int[n];
+        int maxLen = 0;
+        // Iterate through the matrix.
+        for (int i = 0; i < m; i++) {
+            int[] currRow = new int[n];
+            for (int j = 0; j < n; j++) {
+                // Base cases: if we’re in row 0 or column 0, the largest square ending
+                // here has a length of 1. This can be set by using the value in the
+                // input matrix.
+                if (i == 0 || j == 0) {
+                    currRow[j] = matrix[i][j];
+                } else {
+                    if (matrix[i][j] == 1) {
+                        // currRow[j] = 1 + min(left, top-left, top)
+                        currRow[j] = 1 + Math.min(currRow[j - 1], Math.min(prevRow[j - 1], prevRow[j]));
+                    }
+                }
+                maxLen = Math.max(maxLen, currRow[j]);
+            }
+            // Update 'prevRow' with 'currRow' values for the next iteration.
+            prevRow = currRow;
+        }
+        return maxLen * maxLen;
+    }
+}