铁轨问题

#include<iostream>#include<stack>using namespace std;const int maxn=1000;int n,target[maxn];int main(){while(cin>>n){stack<int> s;int A=1,B=1;for(int i=1;i<=n;i++)cin>>target[i];int ok=1;while(B<=n){if(A==target[B]){A++,B++;}else if(!s.empty()&&s.top()==target[B]){s.pop(),B++;}else if(A<=n) s.push(A++);else {ok=0;break;}}cout<<(ok?"Yes":"No")<<endl;}return 0;}