柱状图最大的矩形

public class T84 {
    public int largestRectangleArea(int[] heights) {
        if (heights == null || heights.length == 0) {
            return 0;
        }
        if (heights.length == 1) {
            return heights[0];
        }
        int len = heights.length;
        int[] lefts = new int[len];
        int[] rights = new int[len];
        lefts[0] = -1;
        rights[len - 1] = len;
        for (int i = 1; i < heights.length; i++) {
            int temp = i - 1;
            while (temp >= 0 && heights[temp] >= heights[i]) {
                temp = lefts[temp];
            }
            lefts[i] = temp;
        }
        for (int i = len - 1; i >= 1; i--) {
            int temp = i + 1;
            while (temp < len && heights[temp] >= heights[i]) {
                temp = rights[temp];
            }
            rights[i] = temp;
        }
        int res = 0;
        for (int i = 0; i < len; i++) {
            res = Math.max(res, heights[i] * (rights[i] - lefts[i] - 1));
        }
        return res;
    }
}