codeforces 547B. Mike and Feet 单调栈

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 const int maxn = 2e5+5;
 4 int l[maxn], r[maxn], ans[maxn], a[maxn], q[maxn];
 5 int main()
 6 {
 7     int n;
 8     cin>>n;
 9     for(int i = 1; i<=n; i++) {
10         scanf("%d", &a[i]);
11     }
12     int i = 1, st = 0;
13     while(i<=n) {
14         while(st&&a[q[st-1]]>a[i]) {
15             r[q[st-1]] = i-1;
16             st--;
17         }
18         q[st++] = i;
19         i++;
20     }
21     while(st) {
22         r[q[st-1]] = n;
23         st--;
24     }
25     i = n;
26     while(i>=1) {
27         while(st&&a[q[st-1]]>a[i]) {
28             l[q[st-1]] = i+1;
29             st--;
30         }
31         q[st++] = i;
32         i--;
33     }
34     while(st) {
35         l[q[st-1]] = 1;
36         st--;
37     }
38     memset(ans, 0, sizeof(ans));
39     for(int i = 1; i<=n; i++) {
40         int len = r[i]-l[i]+1;
41         if(ans[len]<a[i]) {
42             ans[len] = a[i];
43         }
44     }
45     for(i = n; i>=1; i--) {
46         if(ans[i]>=ans[i-1])
47             ans[i-1] = ans[i];
48     }
49     for(int i = 1; i<=n; i++) {
50         printf("%d ", ans[i]);
51     }
52 }