铁轨（UVa 514)

　　利用栈实现

C++11 代码如下：

#include<iostream>
#include<stack>
using namespace std;
#define maxn 1001
int n, num[maxn];

int main() {
    while ((cin >> n)&&n!=0) {
        while (n) {
            for (int i = 1; i <= n; i++) {
                cin >> num[i];
                if (num[1] == 0) {
                    n = 0; break;
                }
            }
            if (n == 0)break;
            stack<int>s;
            int A = 1, B = 1;
            bool flag = true;
            while (B <= n) {
                if (A == num[B]) { A++; B++; }
                else if ((!s.empty()) && s.top() == num[B]) { s.pop(); B++; }
                else if (A <= n) s.push(A++);
                else { flag = false; break; }
            }
            cout << (flag ? "Yes" : "No") << endl;
        }
        cout << endl;
    }
    return 0;
}