二分搜索 POJ 3273 Monthly Expense

 1 /*
 2     题意：分成m个集合，使最大的集合值(求和)最小
 3     二分搜索：二分集合大小，判断能否有m个集合。
 4 */
 5 #include <cstdio>
 6 #include <algorithm>
 7 #include <cstring>
 8 #include <cmath>
 9 using namespace std;
10 
11 const int MAXN = 1e5 + 10;
12 const int INF = 0x3f3f3f3f;
13 int a[MAXN];
14 int n, m;
15 
16 bool check(int tot) {
17     int j = 1, sum = 0;
18     for (int i=1; i<=m; ++i)    {
19         sum = 0;
20         while (j <= n && sum + a[j] <= tot)    {
21             sum += a[j++];
22         }
23         if (j == n + 1) return true;
24     }
25     return false;
26 }
27 
28 int main(void)  {       //POJ 3273 Monthly Expense
29     //freopen ("POJ_3273.in", "r", stdin);
30 
31     while (scanf ("%d%d", &n, &m) == 2) {
32         int l = 0, r = 0;
33         for (int i=1; i<=n; ++i)    {
34             scanf ("%d", &a[i]);
35             if (l < a[i])   l = a[i];
36             r += a[i];
37         }
38 
39         while (l < r)   {
40             int mid = (l + r) >> 1;
41             if (check (mid))    r = mid;
42             else    l = mid + 1;
43         }
44         printf ("%d\n", l);
45     }
46 
47     return 0;
48 }