Maximal Rectangle
给一个2d数组, 里面是0和1. 返回最大的全是1的矩形. 这个题和柱状图的最大矩形是一个解法.用largest方法找到一个数组上最大的矩形.
public class Solution {
public int maximalRectangle(char[][] matrix) {
if(matrix == null || matrix.length == 0)
return 0;
int[] hist = new int[matrix[0].length];
int m = matrix.length;
int n = matrix[0].length;
int max = 0;
for(int i = 0 ; i < m; i++) {
for(int j = 0 ; j < n; j++) {
if(matrix[i][j] == '1')
hist[j] ++;
else
hist[j] = 0;
}
max = Math.max(max, largest(hist));
}
return max;
}
public int largest(int[] height) {
if(height == null || height.length == 0)
return 0;
int max = 0;
Stack<Integer> st = new Stack<Integer>();
for(int i = 0 ; i <= height.length; i++) {
int cur = (i == height.length)? 0:height[i];
if(st.empty() || cur > height[st.peek()])
st.push(i);
else{
int tmp = st.pop();
max = Math.max(max, height[tmp] *(st.empty()? i : i - st.peek() - 1) );
i--;
}
}
return max;
}
}