第16周Maximum Length of Repeated Subarray

Maximum Length of Repeated Subarray

Leetcode algorithms problem 718：Maximum Length of Repeated Subarray

• 問題描述

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

• 例子

  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].

• 思路

  dp[i][j] = a[i] == b[j] ? dp[i + 1][j + 1] : 0;
  dp[i][j] : max lenth of common subarray start at a[i] & b[j];

代碼

class Solution {
public:
    int findLength(vector<int>& A, vector<int>& B) {
        vector<int> dp(B.size()+1);
        int res = 0;
        for (int i = A.size() - 1; i >= 0; i--) {
            for (int j = 0; j < B.size(); j++) {
                res = max(res, dp[j] = A[i] == B[j] ? 1 + dp[j + 1] : 0);
            }
        }
        return res;
    }
};

時間複雜度: O(mn)
空間複雜度: O(n)

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