leetcode/541.cpp at dev · xcheng85/leetcode · GitHub

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class Solution {
public:
    string reverseStr(string s, int k) {
        int n = s.size() / (2*k);
        int left = s.size() % (2*k);

        for(int i = 0; i < n; i++){
            int startIndx = 2*k*i;
            int endIndx = 2*k*i + k - 1;

            for(int j = 0; j < k/2; j++){
                char tmp = s[j + startIndx];
                s[j + startIndx] = s[endIndx - j];
                s[endIndx - j] = tmp;
            }
        }

        if(left < k){
            int startIndx = n * 2 * k;
            int endIndx = s.size() - 1;
            for(int j = 0; j < (endIndx - startIndx + 1)/2; j++){
                char tmp = s[j + startIndx];
                s[j + startIndx] = s[endIndx - j];
                s[endIndx - j] = tmp;
            }
        }else{
            int startIndx = n * 2 * k;
            int endIndx = n * 2 * k + k - 1;
            for(int j = 0; j < k/2; j++){
                char tmp = s[j + startIndx];
                s[j + startIndx] = s[endIndx - j];
                s[endIndx - j] = tmp;
            }
        }

        return s;
    }
};