541. Reverse String II

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problem

solution

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class Solution {
public:
    void reverse(string& s, int l, int r ){
        while(l<r) swap(s[l++], s[r--]);
    }
    string reverseStr(string s, int k) {
        for(int i =0;i<s.size() ; i+=2*k){
            reverse(s, i, min(i+k-1, int(s.size()-1)));
        }
        return s;
    }
};

analysis

  • time complexity O(n)
  • space complexity O(1)