51Nod 1272 最大距离 (栈或贪心)

 #include <cstdio>
 #include <queue>
 #include <cstring>
 #include <iostream>
 #include <algorithm>
 #include <stack>
 using namespace std;

 typedef long long ll;
 struct node{int v, id;};
 stack<node>q, sq;

 int main(){
     int n;
     scanf("%d", &n);
     while(!sq.empty())  sq.pop();
     int ans = ;
     for(int i = ;i < n;i++){
         int x;
         scanf("%d", &x);
         node a;
         a.v = x; a.id = i;
         if(sq.size() ==  || sq.top().v > x){
             sq.push(a);
         }
         else{
             while(sq.top().v <= x){
                 ans = max(ans, i - sq.top().id);
                 q.push(sq.top());
                 sq.pop();
                 if(sq.empty())
                     break;
             }
             while(!q.empty()){
                 sq.push(q.top());
                 q.pop();
             }
         }
     }
     printf("%d\n", ans);
     return ;
 }

后来提交一波的时候，最后一组数据超时，于是改用贪心，排序一遍过的：

 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 using namespace std;

 const int maxn = +;
 struct node{
     int id,v;
 }a[maxn];

 bool cmp(node xx,node yy)
 {
     if (xx.v!=yy.v)
     return xx.v<yy.v;
     return xx.id<yy.id;
 }

 int main()
 {
     int n;
     scanf("%d",&n);
     for (int i=;i<n;i++)
     {
         scanf("%d", &a[i].v);
         a[i].id=i;
     }
     sort(a,a+n,cmp);
     int ans = ,Min=a[].id;
     for (int i=;i<n;i++)
     {
         if (a[i].id > Min)
             ans = max(ans, a[i].id-Min);
         else Min = a[i].id;
     }
     printf("%d\n",ans);
     return ;
 }