UVa714 Copying Books (二分法,贪心)

Posted 2020-08-09

链接：http://vjudge.net/problem/UVA-714

 

分析：二分枚举最小值，用贪心的思想每段序列尽量往右划分，注意：因为要求字典序最小解，输出时还有一个贪心过程，左起S[i]尽量小，相当于右起S[j]尽量大，还有一种情况是剩下的数之和已经小于等于ans，但是此时剩余要分配的组数还有多（remain>1）。

 

 1 #include <cstdio>
 2 #include <algorithm>
 3 #include <cstring>
 4 using namespace std;
 5 
 6 const int maxm = 500 + 5;
 7 
 8 int m, k, p[maxm];
 9 
10 int solve(long long maxp) {
11     int ans = 1;
12     long long done = 0;
13     for (int i = 0; i < m; i++) {
14         if (done + p[i] <= maxp) done += p[i];
15         else { done = p[i]; ans++; }
16     }
17     return ans;
18 }
19 
20 int last[maxm];
21 void print(long long ans) {
22     long long done = 0;
23     int remain = k;
24     memset(last, 0, sizeof(last));
25     for (int i = m - 1; i >= 0; i--) {
26         if (done + p[i] > ans || i + 1 < remain) {
27             last[i] = 1; remain--; done = p[i];
28         } else done += p[i];
29     }
30     for (int i = 0; i < m-1; i++) {
31         printf("%d ", p[i]);
32         if (last[i]) printf("/ ");
33     }
34     printf("%d\n", p[m-1]);
35 }
36 
37 int main() {
38     int T;
39     scanf("%d", &T);
40     while (T--) {
41         scanf("%d%d", &m, &k);
42         long long tot = 0;
43         int maxp = -1;
44         for (int i = 0; i < m; i++) {
45             scanf("%d", &p[i]);
46             tot += p[i];
47             maxp = max(maxp, p[i]);
48         }
49         long long L = maxp, R = tot;
50         while (L < R) {
51             long long M = L + (R-L)/2;
52             if (solve(M) <= k) R = M;
53             else L = M+1;
54         }
55         print(L);
56     }
57     return 0;
58 }