1528. Shuffle String

类似快慢指针找cycle O(n) time O(1) space

class Solution {
public:
    string restoreString(string s, vector<int>& indices) {
        for (int i = 0; i < indices.size(); ++i) {
            while (i != indices[i]) { // 只要当前位置不是正确的index就一直swap
                swap(s[i], s[indices[i]]); // 保持字符串跟indices数组同步即可
                swap(indices[i], indices[indices[i]]);
            }
        }
        return s;
    }
};