CF1023D Array Restoration

Posted 2021-01-05 wangyiming

思路：

使用set即可，细节很多，容易出错。

实现：

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 const int INF = 0x3f3f3f3f;
 4 const int MAXN = 200005;
 5 int a[MAXN], l[MAXN], r[MAXN];
 6 int main()
 7 {
 8     int n, q;
 9     while (cin >> n >> q)
10     {
11         for (int i = 1; i <= q; i++) { l[i] = INF; r[i] = -INF; }
12         int c0 = 0, cq = 0;
13         for (int i = 1; i <= n; i++) 
14         {
15             cin >> a[i];
16             c0 += a[i] == 0;
17             cq += a[i] == q;
18             if (a[i] == 0) continue;
19             l[a[i]] = min(l[a[i]], i);
20             r[a[i]] = max(r[a[i]], i);
21         }
22         if (!c0 && !cq) { cout << "NO" << endl; continue; }
23         set<int> st;
24         bool flg = true;
25         for (int i = 1; i <= n; i++)
26         {
27             if (i == l[a[i]]) st.insert(a[i]);
28             if (a[i] && !st.empty() && *st.rbegin() != a[i]) { flg = false; break; }
29             int tmp = -1;
30             if (a[i] == 0)
31             {
32                 if (cq == 0) { tmp = q; cq++; }
33                 else if (!st.empty()) tmp = *st.rbegin();
34                 else tmp = 1;
35             }
36             if (i == r[a[i]]) st.erase(st.find(a[i]));
37             if (tmp != -1) a[i] = tmp;
38         }
39         if (!cq || !flg) { cout << "NO" << endl; continue; }
40         cout << "YES" << endl;
41         for (int i = 1; i <= n; i++) cout << a[i] << " ";
42         cout << endl;
43     }
44     return 0;
45 }