How many times is the same direction selected for each k consecutive direction reversal questions in POJ 3276 turn-on

Source: Internet
Author: User

Face The Right Way
Time Limit: 2000 MS Memory Limit: 65536 K
Total Submissions: 1833 Accepted: 860

Description

Farmer John has arranged his N (1 ≤ N ≤ 5,000) cows in a row and rows of them are facing forward, like good cows. some of them are facing backward, though, and he needs them all to face forward to make his life perfect.

Fortunately, FJ recently bought an automatic cow turning machine. since he purchased the discount model, it must be irrevocably preset to turn K (1 ≤ K ≤ N) cows at once, and it can only turn cows that are all standing next to each other in line. each time the machine is used, it reverses the facing ction of a contiguous group of K cows in the line (one cannot use it on fewer than K cows, e.g ., at the either end of the line of cows ). each cow remains in the same * location * as before, but ends up facing the * opposite direction *. A cow that starts out facing forward will be turned backward by the machine and vice-versa.

Because FJ must pick a single, never-changing value of K, please help him determine the minimum value of K that minimizes the number of operations required by the machine to make all the cows face forward. also determine M, the minimum number of machine operations required to get all the cows facing forward using that value of K.

Input

Line 1: A single integer: N
Lines 2. N + 1: Line I + 1 contains a single character, F or B, indicating whether cow I is facing forward or backward.
Output

Line 1: Two space-separated integers: K and M
Sample Input

7
B
B
F
B
F
B
BSample Output

3 3 Hint

For K = 3, the machine must be operated three times: turn cows (1, 2, 3), (3, 4, 5), and finally (5, 6, 7)
Source

USACO 2007 March Gold
 
Question:
N cows each have a certain direction B back to F indicates the head to you give you a device each time you can choose K consecutive cattle reverse direction ask you how to choose K to make the operand at least k also should be as small as possible

// Train of thought: from the first to find if the current is B, you need to change the I to I + k-1 position // always find n-k + 1 and then judge from n-k + 2 to n whether the meaning of the question is satisfied do not really modify // use a sum value to mark the previous K-1 Modified how many times to determine whether to modify the current use of the ruler acquisition method that is before and after the propulsion # include <stdio. h> # include <string. h> int a [5100], n, flag [5100]; int solve (int k) {int I; memset (flag, 0, sizeof (flag )); // flag [I] indicates the range [I, I + k-1] whether to flip int sum = 0, cnt = 0; // The number of changes in the previous K-1 for (I = 1; I <= n-k + 1; I ++) // sum record goes to the current I, how many times have the previous K-1 been flipped {if (I-k> = 1) {sum-= flag [I-k];} if (a [I] = 0 & sum % 2 = 0) // If it is B and the previous number of times is flipped even, you still need to flip {flag [I] = 1; sum + = flag [I]; cnt ++ ;} else if (a [I] = 1 & sum % 2 = 1) // if it is F and the previous number of times is flipped {flag [I] = 1; sum + = flag [I]; cnt ++;} // printf ("I = % d flag [I] = % d \ n", I, flag [I]) ;}for (I; I <= n; I ++) {if (I-k> = 1) {sum-= flag [I-k];} if (sum % 2 = 0 & a [I] = 0) return-1; else if (sum % 2 = 1 & a [I] = 1) return-1;} return cnt ;}int main () {int I, k, mn; char s [2]; while (scanf ("% d", & n )! = EOF) {mn = 100010000; for (I = 1; I <= n; I ++) {scanf ("% s", s ); if (s [0] = 'B') a [I] = 0; else if (s [0] = 'F') a [I] = 1 ;} k = 1; for (I = 1; I <= n; I ++) {int mid = solve (I); // printf ("k = % d, cnt = % d \ n ", I, mid); if (mid =-1) continue; if (mn> mid) {mn = mid; k = I ;}} printf ("% d \ n", k, mn);} return 0 ;}

 

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.