二分搜索 POJ 3273 Monthly Expense

 /*
题意：分成m个集合，使最大的集合值(求和)最小
二分搜索：二分集合大小，判断能否有m个集合。
*/
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <cmath>
using namespace std;

const int MAXN = 1e5 + 10;
const int INF = 0x3f3f3f3f;
int a[MAXN];
int n, m;

bool check(int tot) {
int j = 1, sum = 0;
for (int i=1; i<=m; ++i)    {
sum = 0;
while (j <= n && sum + a[j] <= tot)    {
sum += a[j++];
}
if (j == n + 1) return true;
}
return false;
}

int main(void)  {       //POJ 3273 Monthly Expense
//freopen ("POJ_3273.in", "r", stdin);

while (scanf ("%d%d", &n, &m) == 2) {
int l = 0, r = 0;
for (int i=1; i<=n; ++i)    {
scanf ("%d", &a[i]);
if (l < a[i])   l = a[i];
r += a[i];
}

while (l < r)   {
int mid = (l + r) >> 1;
if (check (mid))    r = mid;
else    l = mid + 1;
}
printf ("%d\n", l);
}

return 0;
}