# 【題解】ZeroJudge c123: 00514 – Rails

```#include <iostream>
#include <stack>

using namespace std;

int main() {
int n;
while (cin >> n && n){
while (1){
int a[n], point = 1;
stack <int> stk;
cin >> a[0];
if (a[0] == 0) break;
for (int i = 1; i < n; i++){
cin >> a[i];
}
int i;
for (i = 0; i < n; i++){
if (!stk.empty() && stk.top() == a[i]){
stk.pop();
}else if (a[i] >= point){
for (int j = point; j < a[i]; j++){
stk.push(j);
}
point = a[i] + 1;
}else{
break;
}
}
if (i == n){
cout << "Yes" << endl;
}else{
cout << "No" << endl;
}
}
cout << endl;
}
return 0;
}
```

Python 程式碼 (2019-08-06)

```while True:
n = int(input())
if n == 0:
break
while True:
nums = list(map(int, input().split()))
if len(nums) == 1 and nums[0] == 0:
break
station = [0]
a = []
flag = True
for i in range(1, n+1):
a.append(i)
for num in nums:
while True:
if num == station[-1]:
station.pop()
break
elif num > station[-1]:
station.append(a.pop(0))
elif num < station[-1]:
flag = False
break
if not flag:
print('No')
break
else:
print('Yes')
```