POJ 3273 Monthly Expense 二分

我们对每个月花费的最小花费进行二分，对于每一次二分的值mid，计算能花的月份数量，如果月份数量小于等于m，我们就不断的缩小mid，直到找到月份数量小于等于m 与 月份数量大于m的临界值，取最后一次满足条件的mid，输出即可。

#include 
using namespace std;
int arr[100007], n, m, maxt = 0;
void input()
{
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n; i++)
    {
        scanf("%d", &arr[i]);
        maxt = max(maxt, arr[i]);
    }
}
bool judge(int mid)
{
    int count = 0, current = mid;
    for (int i = 1; i <= n; i++)
    {
        if (current == arr[i])
        {
            current = mid;
            count++;
        }
        else if (current < arr[i])
        {
            current = mid - arr[i];
            count++;
        }
        else
        {
            current = current - arr[i];
        }
    }
    if (current != mid)
    {
        count++;
    }
    return count <= m;
}
void binarySearch()
{
    int left = maxt - 1, right = 1000000001;
    while (left + 1 < right)
    {
        int mid = (left + right) / 2;
        if (judge(mid))
        {
            right = mid;
        }
        else
        {
            left = mid;
        }
    }
    printf("%d\n", right);
}
int main()
{
    input();
    binarySearch();
    return 0;
}