POJ3273:Monthly Expense(二分)

Monthly Expense

Time Limit: 2000MS		Memory Limit: 65536K
Total Submissions: 9302		Accepted: 3823

Description

Farmer John is an astounding accounting wizard and has realized he might run out of money to run the farm. He has already calculated and recorded the exact amount of money (1 ≤money_i ≤ 10,000) that he will need to spend each day over the nextN (1 ≤ N ≤ 100,000) days.

FJ wants to create a budget for a sequential set of exactlyM (1 ≤M ≤ N) fiscal periods called "fajomonths". Each of these fajomonths contains a set of 1 or more consecutive days. Every day is contained in exactly one fajomonth.

FJ's goal is to arrange the fajomonths so as to minimize the expenses of the fajomonth with the highest spending and thus determine his monthly spending limit.

Input

Line 1: Two space-separated integers:N andM
Lines 2..N+1: Line i+1 contains the number of dollars Farmer John spends on theith day

Output

Line 1: The smallest possible monthly limit Farmer John can afford to live with.

Sample Input

7 5
100
400
300
100
500
101
400

Sample Output

500

Hint

If Farmer John schedules the months so that the first two days are a month, the third and fourth are a month, and the last three are their own months, he spends at most $500 in any month. Any other method of scheduling gives a larger minimum monthly limit.

Source

USACO 2007 March Silver

MYCode:

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
#define MAX 100010
int v[MAX];
int sum;
int n,m;
int most;
bool check(int lim)
{
    int i;
    int s=0;
    int ct=0;
    for(i=1;i<=n;i++)
    {
        if(s+v[i]<=lim)
        s+=v[i];
        else
        {
            ct++;
            s=v[i];
        }
    }
    ct++;
    if(ct<=m)
    return true;
    return false;
}

int search()
{
    int lt=most,rt=sum;
    while(lt<rt)
    {
        int mid=(lt+rt)/2;
        if(check(mid))
        rt=mid;
        else
        lt=mid+1;
    }
    return rt;
}
int main()
{
    while(scanf("%d%d",&n,&m)!= EOF)
    {
        int i;
        sum=0;
        most=-1;
        for(i=1;i<=n;i++)
        {
            scanf("%d",&v[i]);
            sum+=v[i];
            if(v[i]>most)
            most=v[i];
        }
        int ans=search();
        printf("%d\n",ans);
    }
}

//63MS

二分法,复杂度nlogn