二分搜索 POJ 3273 Monthly Expense

题目传送门

/*
    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
", l);
    }

    return 0;
}