[UVA][二分搜+greedy] 907 - Winterim Backpacking Trip＠Morris' Blog｜PChome Online 人新台

Morris' Blog 我在摸索我存在的意、生命的意、涵及值。有真正神手般的害，套用模式是大部分的情。那害的我存在的意何，托出神的存在？有候不能怪人不我，我已始省思，什我有人的原因，而是全要靠人。有候我我不同，那是因我做不到很多人能到的事情。我不到、玩不起、得不明、理解得不多，我缺少的文能力，就是一切一切能的判定。此，我不得能做些人有助的事情。我知道我自己是不服的性格，但在我不得不。我有能力，因此我必。我到底世界作什？充不定性，而我是法出拔萃，想一般人似乎也回不了了。越大的挑需要越力的支持，而我的支持是什？最近人，但都是失的局，人能接受，不需要言，不需要通，一切所想都表不出。
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2013-01-27 08:37:24| 人1,497| 回3 | 上一篇 | 下一篇

[UVA][二分搜+greedy] 907 - Winterim Backpacking Trip

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Problem C

Winterim Backpacking Trip

This Winter we are going on a trip along the Appalachian Trail. The trail is a continuous marked footpath that goes from Katahdin in Maine to Springer Mountain in Georgia, a distance of about 2160 miles. Even though our trip will only consider some part of the trail, it will be our first real backpacking experience and an excellent opportunity to acquire winter camping skills.

Part of the experience is also the route planning of the trip. We have a list of all possible campsites that we can use along the way and we want to do this trip so that we only stop K nights to camp. We also know in advance the distance between consecutive campsites and we are only allowed to camp at a campsite. Our goal is to plan the trip so that we minimise the maximum amount of walking done in a single day. In other words, if our trip involves 2 nights (3 days of walking), and we walk 9, 10, 5 miles on each day respectively, the cost (maximum amount of walking done in one day) is 10. Another schedule that involves walking 9, 6, 9 miles on each day has cost 9.

Problem

Given the distances between N consecutive campsites of a trail and given the number of nights for your trip, K, your task is to devise a camping strategy for the specified trail such that it minimises the maximum amount of walking done in a single day. Note that the first distance value given is the distance from our start-point of the trail to our 1st campsite, and the last distance value given is the distance from our Nth campsite to our end-point of the trail.

Input

The input file contains several test cases, each of them as describes below.
The first line of input consists of two numbers, the number of campsites (0 < N <= 600) and the number of nights of the trip (0 <= K <= 300). The following N+1 input lines indicate the distance in miles between consecutive campsite locations.

Output

For each test case, on a line by itself, your program must output the maximum amount of walking in a single day for the route that minimises such value.

Sample Input

4 3 7 2 6 4 5

Sample Output

的另外一方法是 DP，效率 O(N*N*K)

那使用二分搜答案，使用 O(n) 去，效率 O(N*log(ans))




#include <stdio.h>
int A[605], n, m;
int check(int res) {
 int sum = 0, cnt = 0, i;
 for(i = 0; i <= n; i++) {
 if(A[i] > res) return 0;
 if(sum+A[i] > res)
 sum = A[i], cnt++;
 else
 sum += A[i];
 }
 if(sum) cnt++;
 return cnt <= m;
}
int main() {
 int i;
 while(scanf("%d %d", &n, &m) == 2) {
 n++, m++;
 for(i = 0; i < n; i++)
 scanf("%d", &A[i]);
 int l = 0, r = 1000000, mid;
 while(l <= r) {
 mid = (l+r)/2;
 if(check(mid))
 r = mid-1;
 else
 l = mid+1;
 }
 printf("%d\n", r+1);
 }
 return 0;
}