算法问题——柱形图的面试盛水问题

容器盛水问题：​​https://www.nowcoder.com/practice/31c1aed01b394f0b8b7734de0324e00f?tpId=117&&tqId=35269&rp=1&ru=/ta/job-code-high&qru=/ta/job-code-high/question-ranking​​

​​11. 盛最多水的容器​​

class Solution {
    public int maxArea(int[] height) {
        int l = 0, r = height.length - 1;
        int ans = 0;
        while (l < r) {
            int area = Math.min(height[l], height[r]) * (r - l);
            ans = Math.max(ans, area);
            if (height[l] <= height[r]) {
                ++l;
            } else {
                --r;
            }
        }
        return ans;
    }
}

​​84. 柱状图中最大的矩形​​

class Solution {
    public int largestRectangleArea(int[] heights) {
        int len = heights.length;
        if (len == 0) {
            return 0;
        }
        if (len == 1) {
            return heights[0];
        }
        int Area = 0;
        int[] newHeights = new int[len + 2];
        for (int i = 0; i < len; i++) {
            newHeights[i + 1] = heights[i];
        }
        len += 2;
        heights = newHeights;
        //栈中存放的是一个宽度的位置 当前位置的最高下标值 
        Deque<Integer> stack = new ArrayDeque<>();
        stack.add(0);
        for (int i = 1; i < len; i++) {
            //当栈顶的元素大于当前的元素
            while (heights[stack.peekLast()] > heights[i]) {
                //栈顶的高度
                int height = heights[stack.removeLast()];
                //弹出栈
                int width = i - stack.peekLast() - 1;
                Area = Math.max(Area, width * height);
            }
            stack.add(i);
        }
        return Area;
    }
}