[Swift]LeetCode962. 最大宽度坡 | Maximum Width Ramp

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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

---

给定一个整数数组 A，坡是元组 (i, j)，其中  i < j 且 A[i] <= A[j]。这样的坡的宽度为 j - i。

找出 A 中的坡的最大宽度，如果不存在，返回 0 。

示例 1：

输入：[6,0,8,2,1,5]
输出：4
解释：
最大宽度的坡为 (i, j) = (1, 5): A[1] = 0 且 A[5] = 5.

示例 2：

输入：[9,8,1,0,1,9,4,0,4,1]
输出：7
解释：
最大宽度的坡为 (i, j) = (2, 9): A[2] = 1 且 A[9] = 1.

提示：

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

---

440ms 

class Solution {
    func maxWidthRamp(_ A: [Int]) -> Int {
        var val:[Int] = [Int]()
        var index:[Int] = [Int]()
        var n:Int = A.count
        var ans:Int = 0
        for i in 0..<n
        {
            var x:Int = A[i]
            var left:Int = 0
            var right:Int = val.count - 1
            while(left < right)
            {
                var mid:Int = (left + right) / 2
                if val[mid] <= x
                {
                    right = mid
                }
                else
                {
                    left = mid + 1
                }
            }
            if left <= right && val[left] <= x
            {
                ans = max(ans, i - index[left])
            }
            if val.isEmpty || val.last! > x
            {
                val.append(x)
                index.append(i)
            }
        }
        return ans
    }
}

---

528ms

class Solution 
{
    
    struct IndexedValue
    {
        let index: Int
        let value: Int
        
        init( _ index: Int, _ value: Int )
        {
            self.index = index
            self.value = value
        }
    }
    
    func maxWidthRamp( _ values: [ Int ] ) -> Int 
    {
        var indexedValues: [ IndexedValue ] = []
        for index in ( 0 ..< values.count )
        {
            
            indexedValues.append( IndexedValue( index, values[ index ] ) )
            
        }
        indexedValues.sort( 
            by: 
            { 
                if $0.value == $1.value
                {
                    return $0.index < $1.index
                }
                else
                {
                    return $0.value <= $1.value
                }
            } 
        )
        
        var minIndex: Int = indexedValues[ 0 ].index
        var maxRamp: Int = 0
        
        for indexedValue in indexedValues
        {
            if indexedValue.index < minIndex
            {
                minIndex = indexedValue.index
            }
            else
            {
                let ramp: Int = ( indexedValue.index - minIndex )
                maxRamp = max( maxRamp, ramp )
            }
        }
        
        return maxRamp
    }
}

---

1252ms

class Solution {
    func maxWidthRamp(_ A: [Int]) -> Int {
        var numbers: [[Int]] = Array(repeating: [], count: 50001)
        for (i, a) in A.enumerated() {
            numbers[a] = numbers[a] + [i]
        }
        var res: [Int] = []
        for i in (0...50000) {
            res += numbers[i]
        }
        
        var dist = 0
        var minN = Int.max
        for i in (0..<res.count) {
            if res[i] < minN {
                minN = res[i]
            } else {
                dist = max(dist, res[i] - minN)
            }
        }
        
        
        return dist
    }
}