int find_max_matrix(int A[ROW][COL])
{
int i, j;
int max, cur_max;
cur_max = 0;
//Calculate Auxilary matrix
for (i=1; i<ROW; i++)
for(j=0; j<COL; j++)
{
if(A[i][j] == 1)
A[i][j] = A[i-1][j] + 1;
}
//Calculate maximum area in S for each row
for (i=0; i<ROW; i++)
{
max = largestArea(A[i], COL);
if (max > cur_max)
cur_max = max;
}
//Regenerate Oriignal matrix
for (i=ROW-1; i>0; i--)
for(j=0; j<COL; j++)
{
if(A[i][j])
A[i][j] = A[i][j] - A[i-1][j];
}
return cur_max;
}
int largestArea(vector<int>& heights, int start, int end)
{
if (start > end)
return 0;
if (start == end)
return heights[start];
int minHeight = heights[start];
int minIndex = start;
bool sorted = true;
for (int i = start+1; i <= end; ++i)
{
if (heights[i] < heights[i-1])
sorted = false;
if (minHeight > heights[i])
{
minHeight = heights[i];
minIndex = i;
}
}
if (sorted)
{
int _max = 0;
for (int i = start; i <= end; i++) {
_max = max(_max, heights[i] * (end - i + 1));
}
return _max;
}
int maxArea = (end-start+1) * minHeight;
int leftIndex = minIndex-1;
while (start <= leftIndex && heights[leftIndex] == heights[minIndex])
leftIndex--;
int rightIndex = minIndex+1;
while (rightIndex <= end && heights[rightIndex] == heights[minIndex])
rightIndex++;
int leftArea = largestArea(heights, start, leftIndex);
int rightArea = largestArea(heights, rightIndex, end);
maxArea = max(maxArea, leftArea);
maxArea = max(maxArea, rightArea);
return maxArea;
}
/*
* Method1: O(n*logn) complecity
*/
int largestRectangleArea(vector<int>& heights) {
if (heights.size() == 0)
return 0;
int area = largestArea(heights, 0, heights.size()-1);
return area;
}
