84. Largest Rectangle in Histogram

    /** 84. Largest Rectangle in Histogram * 2016-5-13 by Mingyang* 这里并不需要两个stack，只需要一个stack，装的是递增序列的index* 直到遇到一个递减的时候，弹出来，求一个一个的面积大小* 不过注意的是最后如果以递增的序列结尾的话，还需要一个一个的求完*/public int largestRectangleArea(int[] height) {if (height == null || height.length == 0) {return 0;} Stack<Integer> stack = new Stack<Integer>();     int max = 0;int i = 0; while (i < height.length) {//push index to stack when the current height is larger than the previous oneif (stack.isEmpty() || height[i] >= height[stack.peek()]) {stack.push(i);i++;} else {//calculate max value when the current height is less than the previous oneint p = stack.pop();int h = height[p];int w = stack.isEmpty() ? i : i - stack.peek() - 1;max = Math.max(h * w, max);}     } while (!stack.isEmpty()) {int p = stack.pop();int h = height[p];int w = stack.isEmpty() ? i : i - stack.peek() - 1;max = Math.max(h * w, max);} return max;}