Add 85_Maximal_Rectangle.java

Author: Sean Prashad

Matrix/85_Maximal_Rectangle.java

@@ -0,0 +1,46 @@
+class Solution {
+ public int maximalRectangle(char[][] matrix) {
+ if (matrix == null || matrix.length == 0) {
+ return 0;
+ }
+
+ int[] heights = new int[matrix[0].length];
+ int max = 0;
+
+ for (int i = 0; i < matrix.length; i++) {
+ for (int j = 0; j < matrix[i].length; j++) {
+ if (matrix[i][j] == '0') {
+ heights[j] = 0;
+ } else {
+ heights[j] += 1;
+ }
+ }
+
+ int area = largestRectangleArea(heights);
+ max = Math.max(max, area);
+ }
+
+ return max;
+ }
+
+ private int largestRectangleArea(int[] heights) {
+ int n = heights.length;
+ int max = 0;
+ Stack<Integer> s = new Stack<>();
+
+ for (int i = 0; i <= n; i++) {
+ int h = i == n ? 0 : heights[i];
+
+ while (!s.isEmpty() && heights[s.peek()] > h) {
+ int currHeight = heights[s.pop()];
+ int leftBoundary = s.isEmpty() ? -1 : s.peek();
+ int rightBoundary = i - 1;
+ max = Math.max(max, currHeight * (rightBoundary - leftBoundary));
+ }
+
+ s.push(i);
+ }
+
+ return max;
+ }
+}