[Swift]LeetCode363. 矩形区域不超过 K 的最大数值和 | Max Sum

发布时间：2020-12-14 05:05:46 所属栏目：百科来源：网络整理

导读：Given a non-empty 2D matrix? matrix ?and an integer? k ,find the max sum of a rectangle in the? matrix ?such that its sum is no larger than? k . Example: Input: matrix = [[1,1],[0,-2,3]],k = 2 Output: 2 Explanation:?Because the sum of rect

Given a non-empty 2D matrix?matrix?and an integer?k,find the max sum of a rectangle in the?matrix?such that its sum is no larger than?k.

Example:

Input: matrix = [[1,1],[0,-2,3]],k = 2 Output: 2 Explanation:?Because the sum of rectangle  is 2,? and 2 is the max number no larger than k (k = 2).[[0,[-2,3]]

Note:

The rectangle inside the matrix must have an area > 0.
What if the number of rows is much larger than the number of columns?

给定一个非空二维矩阵?matrix?和一个整数?k，找到这个矩阵内部不大于?k的最大矩形和。

示例:

输入: matrix = [[1,k = 2
输出: 2 
解释:?矩形区域??的数值和是 2，且 2 是不超过 k 的最大数字（k = 2）。
[[0,3]]

说明：

矩阵内的矩形区域面积必须大于 0。
如果行数远大于列数，你将如何解答呢？

13108ms

 1 class Solution {
 2     func maxSumSubmatrix(_ matrix: [[Int]],_ k: Int) -> Int {
 3         if matrix.isEmpty || matrix[0].isEmpty {return 0}
 4         var m:Int = matrix.count
 5         var n:Int = matrix[0].count
 6         var res:Int = Int.min
 7         var sum:[[Int]] = [[Int]](repeating:[Int](repeating:0,count:n),count:m)
 8         for i in 0..<m
 9         {
10             for j in 0..<n
11             {
12                 var t:Int = matrix[i][j]
13                 if i > 0 {t += sum[i - 1][j]}
14                 if j > 0 {t += sum[i][j - 1]}
15                 if i > 0 && j > 0 {t -= sum[i - 1][j - 1]}
16                 sum[i][j] = t
17                 for r in 0...i
18                 {
19                     for c in 0...j
20                     {
21                         var d:Int = sum[i][j]
22                         if r > 0 {d -= sum[r - 1][j]}
23                         if c > 0 {d -= sum[i][c - 1]}
24                         if r > 0 && c > 0 {d += sum[r - 1][c - 1]}
25                         if d <= k {res = max(res,d)}
26                     }
27                 }
28             }
29         }
30         return res
31     }
32 }

（编辑：李大同）

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