题目：详见uva514.
此题就是输入1~n的任意一种顺序组合，问能否通过1,2,3,……n转换为此组合。
此题的C铁轨其实就是栈，特点是后进先出，通过栈能够改变数字的顺序。
参考代码：
#include <iostream>
#include <cstring>
#include <stack>
using namespace std;
int rail[1005];
void yesandno(int rail[],int n) {
stack<int> s;
int flag = 1;
int a = 1,b = 1;
while (b <= n) {
if (a == rail[b]) {
a++;
b++;
}
else if (!s.empty() && s.top() == rail[b]) {
s.pop();
b++;
}
else if (a <= n) {
s.push(a++);
}
else {
flag = 0;
break;
}
}
if (flag == 1) {
cout << "Yes" << endl;
}
else {
cout << "No" << endl;
}
}
int main() {
int n;
while (cin >> n && n) {
for (int i = 1;i <= n;++i) {
cin >> rail[i];
if (rail[i] == 0) {
cout << endl;
break;
}
if (i == n) {
yesandno(rail,n);
i = 0;
memset(rail,0,sizeof(rail));
}
}
}
return 0;
}
