• Time:O(n)
• Space:O(n)

## C++

``````class Solution {
public:
string pushDominoes(string dominoes) {
int L = -1;
int R = -1;

for (int i = 0; i <= dominoes.length(); ++i)
if (i == dominoes.length() || dominoes[i] == 'R') {
if (L < R)
while (R < i)
dominoes[R++] = 'R';
R = i;
} else if (dominoes[i] == 'L') {
if (R < L || L == -1 && R == -1) {
if (L == -1 && R == -1)
++L;
while (L < i)
dominoes[L++] = 'L';
} else {
int l = R + 1;
int r = i - 1;
while (l < r) {
dominoes[l++] = 'R';
dominoes[r--] = 'L';
}
}
L = i;
}

return dominoes;
}
};
``````

## JAVA

``````class Solution {
public String pushDominoes(String dominoes) {
char[] s = dominoes.toCharArray();
int L = -1;
int R = -1;

for (int i = 0; i <= dominoes.length(); ++i)
if (i == dominoes.length() || s[i] == 'R') {
if (L < R)
while (R < i)
s[R++] = 'R';
R = i;
} else if (s[i] == 'L') {
if (R < L || L == -1 && R == -1) {
if (L == -1 && R == -1)
++L;
while (L < i)
s[L++] = 'L';
} else {
int l = R + 1;
int r = i - 1;
while (l < r) {
s[l++] = 'R';
s[r--] = 'L';
}
}
L = i;
}

return new String(s);
}
}
``````

## Python

``````class Solution:
def pushDominoes(self, dominoes: str) -> str:
ans = list(dominoes)
L = -1
R = -1

for i in range(len(dominoes) + 1):
if i == len(dominoes) or dominoes[i] == 'R':
if L < R:
while R < i:
ans[R] = 'R'
R += 1
R = i
elif dominoes[i] == 'L':
if R < L or (L, R) == (-1, -1):
if (L, R) == (-1, -1):
L += 1
while L < i:
ans[L] = 'L'
L += 1
else:
l = R + 1
r = i - 1
while l < r:
ans[l] = 'R'
ans[r] = 'L'
l += 1
r -= 1
L = i

return ''.join(ans)
``````