Given a 2D binary matrix filled with 0’s and 1’s, find the largest rectangle containing all ones and return its area.
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| public class MaximalRectangle {
public int maximalRectangle(char[][] matrix) {
if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
return 0;
}
int[][] map = new int[matrix.length][matrix[0].length + 1];
for (int i = 0; i < matrix.length; i++) {
for (int j = 0; j < matrix[0].length; j++) {
if (matrix[i][j] == '0') {
map[i][j] = 0;
} else {
map[i][j] = i == 0 ? 1 : map[i - 1][j] + 1;
}
}
}
int max = 0;
for (int i = 0; i < matrix.length; i++) {
int value = helper(map[i]);
max = Math.max(max, value);
}
return max;
}
public int helper(int[] height) {
if (height == null || height.length == 0) {
return 0;
}
Stack<Integer> stack = new Stack<Integer>();
int crt = 0;
int max = 0;
while (crt < height.length) {
if (stack.isEmpty() || height[crt] >= height[stack.peek()]) {
stack.push(crt++);
} else {
int i = stack.pop();
max = Math.max(max, height[i] * (stack.isEmpty() ? crt : crt - stack.peek() - 1));
}
}
return max;
}
}
|