hdu 3415 Max Sum of Max-K-sub-sequence
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:
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
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