微软滑动窗口双指针面试题Leetcode424/1156

Given an array with around 10w elements, each element is within [0,10w], how to get max subsequense length with same value if you have a opportunity to swap two elements?

Sampes:
1,1,0,2,3,1,0,1,1,3,4 => output: 4
0,2,3,1,0,1,1,3,4 => output: 3
1,1,0,0,2,3,3,1 => output: 3

 

这道题目参考Leetcode 1156. 单字符重复子串的最大长度

而这道题的思路是用Leetcode 424. 替换后的最长重复字符 的思路改造过来，不是直接进行交换，而是最后特判一下是否一定能交换。

Leetcode 424

class Solution {
public:
    int characterReplacement(string s, int k) {
        // 维护一个滑动窗口i,j
        // 维护这个滑动窗口中出现次数最多的元素（需要HashMap以及一个变量）
        // 这个窗口的大小一定小于maxLen+k
        int maxlength = 0;
        int Hash[26] = {0};
        int maxLen = 0, res = 0;    
        for(int i=0,j=0;j<s.size();j++){
            Hash[s[j]-'A']++;
            maxLen = max(maxLen, Hash[s[j]-'A']);
            while(i<j && j-i+1-maxLen>k)
                Hash[s[i++]-'A']--;
            res = max(res,j-i+1);
        }
        return res;
    }
};

 

Leetcode 1156

class Solution {
public:
    int maxRepOpt1(string s) {
        int maxlength = 0;
        int Hash[26] = {0};
        int maxLen = 0, res = 0, k =1;
        for(int i=0,j=0;j<s.size();j++){
            Hash[s[j]-'a']++;
            maxLen = max(maxLen, Hash[s[j]-'a']);
            while(i<j && j-i+1-maxLen>k)
                Hash[s[i++]-'a']--;
            res = max(res,j-i+1);
        }
        int hashmap[26] = {0};
        maxLen = 0;
        for(auto c:s) {
            hashmap[c-'a']++;
            maxLen = max(maxLen,hashmap[c-'a']);
        }
        return min(maxLen,res);

    }
};

 

来源：oschina

链接：https://my.oschina.net/u/4266314/blog/4540334