hdu 3415 Max Sum of MaxKsubsequence

http://acm.hdu.edu.cn/showproblem.php?pid=3415

　　不难的单调队列，不过刚开始的时候开的队列不够大，所以数组越界了。不过最不解的是hdu返回的是wa而不是runtime error，搞到我以为是单调队列写错什么了，所以不停debug，debug了好多组数据，最终才想到队列的大小是会超出n的，于是改过来以后就ac了！

　　时间相当理想，才46ms！

下面是我的代码：

View Code

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <cstdlib>
 4 
 5 const int maxn = 100001;
 6 const int inf = 0x7fffffff;
 7 int q[maxn << 1], ind[maxn << 1], qh, qt;
 8 int begin, end, sv[maxn];
 9 
10 void scan(int &n){
11     char ch;
12 
13     while ((ch = getchar()) != '-' && ('0' > ch || ch > '9'));
14     if (ch != '-'){
15         n = ch - '0';
16         while ((ch = getchar()) >= '0' && ch <= '9')
17             n = n * 10 + ch - '0';
18     }
19     else{
20         n = 0;
21         while ((ch = getchar()) >= '0' && ch <= '9')
22             n = n * 10 + '0' - ch;
23     }
24 }
25 
26 int main(){
27 #ifndef ONLINE_JUDGE
28     freopen("in", "r", stdin);
29 #endif
30     int N;
31     int n, k, sum, tmp, maxsum, ci;
32 
33     scan(N);
34     while (N--){
35         scan(n); scan(k);
36 
37         qh = sum = begin = q[0] = 0;
38         qt = 1;
39         ind[0] = -1;
40         maxsum = -inf;
41         end = n;
42 
43         for (int i = 0; i < n; i++){
44             scan(sv[i]);
45             sum += sv[i];
46             if (i - ind[qh] > k) qh++;
47 
48             tmp = sum - q[qh];
49             if (tmp > maxsum){
50                 maxsum = tmp;
51                 begin = ind[qh] + 1;
52                 end = i;
53             }
54             while (qh < qt && q[qt - 1] >= sum) qt--;
55             q[qt] = sum;
56             ind[qt++] = i;
57         }
58 
59         for (int i = 0; i < k; i++){
60             ci = i + n;
61 
62             sum += sv[i];
63             if (ci - ind[qh] > k) qh++;
64 
65             tmp = sum - q[qh];
66             if (tmp > maxsum){
67                 maxsum = tmp;
68                 begin = ind[qh] + 1;
69                 end = ci;
70             }
71             while (qh < qt && q[qt - 1] >= sum) qt--;
72             q[qt] = sum;
73             ind[qt++] = ci;
74         }
75 
76         printf("%d %d %d\n", maxsum, begin % n + 1, end % n + 1);
77     }
78 
79     return 0;
80 }

——written by Lyon