[Swift]LeetCode718. 最长重复子数组 | Maximum Length of Repeated Subarray

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Given two integer arrays A and B, return the maximum length of an subarray that appears in both arrays.

Example 1:

Input:
A: [1,2,3,2,1]
B: [3,2,1,4,7]
Output: 3
Explanation: 
The repeated subarray with maximum length is [3, 2, 1]. 

Note:

1. 1 <= len(A), len(B) <= 1000
2. 0 <= A[i], B[i] < 100

---

给两个整数数组 A 和 B ，返回两个数组中公共的、长度最长的子数组的长度。

示例 1:

输入:
A: [1,2,3,2,1]
B: [3,2,1,4,7]
输出: 3
解释: 
长度最长的公共子数组是 [3, 2, 1]。

说明:

1. 1 <= len(A), len(B) <= 1000
2. 0 <= A[i], B[i] < 100

---

308ms

class Solution {
    func findLength(_ A: [Int], _ B: [Int]) -> Int {
        var ret = 0
        let lenA = A.count, lenB = B.count
        for k in 1..<(lenA + lenB) {
            var i = max(0, lenA - k)
            var j = max(0, k - lenA)
            var len = 0
            while i < lenA && j < lenB {
                len = (A[i] == B[j]) ? (len + 1) : 0
                ret = max(ret, len)
                i += 1
                j += 1
            }
        }
        return ret
    }
}

---

1304ms

class Solution {
    func findLength(_ A: [Int], _ B: [Int]) -> Int {
        let m = A.count, n = B.count
        var res = 0
        
        var dp = [[Int]](repeating:[Int](repeating: 0, count: n+1), count: m + 1)
        
        for i in 1...m {
            for j in 1...n {
                if A[i-1] == B[j-1] {
                    dp[i][j] = 1 + dp[i-1][j-1]
                    res = max(res, dp[i][j])
                }
            }
        }
        return res
    }
}

---

Runtime: 2028 ms

Memory Usage: 25.4 MB

class Solution {
    func findLength(_ A: [Int], _ B: [Int]) -> Int {
        var res:Int = 0
        var dp:[[Int]] = [[Int]](repeating:[Int](repeating:0,count:B.count + 1),count:A.count + 1)
        for i in 1..<dp.count
        {
            for j in 1..<dp[i].count
            {
                dp[i][j] = (A[i - 1] == B[j - 1]) ? dp[i - 1][j - 1] + 1 : 0
                res = max(res, dp[i][j])
            }
        }
        return res
    }
}