21-push-dominoes.cpp

// https://leetcode-cn.com/problems/push-dominoes/

class Solution {
public:
    string pushDominoes(string dominoes) {
        int n = dominoes.size(), i = 0;
        char left = 'L';
        while (i < n) {
            auto j = i;
            while (j < n && dominoes[j] == '.') {
                j++;
            }
            char right = j < n ? dominoes[j] : 'R';
            if (left == right) {
                while (i < j) {
                    dominoes[i++] = left;
                }
            } else if (left=='R'&&right=='L'){
                auto k = j-1;
                while (i<k){
                    dominoes[i++]='R';
                    dominoes[k--]='L';
                }
            }
            left = right;
            i=j+1;
        }
        return dominoes;
    }
};