# 962. Maximum Width Ramp 最大宽度坡

@TOC

## # 题目描述

Given an array `A` of integers, a ramp is a tuple `(i, j)` for which `i < j` and `A[i] <= A[j]`. The width of such a ramp is `j - i`.

Find the maximum width of a ramp in `A`. If one doesn't exist, return 0.

Example 1:

``````Input: [6,0,8,2,1,5]
Output: 4
Explanation:
The maximum width ramp is achieved at (i, j) = (1, 5): A[1] = 0 and A[5] = 5.
``````

Example 2:

``````Input: [9,8,1,0,1,9,4,0,4,1]
Output: 7
Explanation:
The maximum width ramp is achieved at (i, j) = (2, 9): A[2] = 1 and A[9] = 1.
``````

Note:

1. 2 <= A.length <= 50000
2. 0 <= A[i] <= 50000

## # 解题方法

### # 单调栈

python代码如下：

``````class Solution(object):
def maxWidthRamp(self, A):
"""
:type A: List[int]
:rtype: int
"""
N = len(A)
stack = []
res = 0
for i, a in enumerate(A):
if not stack or stack[-1][1] > a:
stack.append((i, a))
else:
x = len(stack) - 1
while x >= 0 and stack[x][1] <= a:
res = max(res, i - stack[x][0])
x -= 1
return res
``````

## # 日期

2018 年 12 月 23 日 —— 周赛成绩新高