poj 3273 Monthly Expense

给出一组数据，最大值为left，和为right。在[left，right]区间进行二分！！！

代码：

 

#include<iostream>
#include<stdio.h>
#include<algorithm>
#include<iomanip>
#include<cmath>
#include<cstring>
#include<vector>
#define ll __int64
#define pi acos(-1.0)
#define MAX 50000
using namespace std;
int an[100005];
int main(){
    int n,m,i,sum,left,right=0,mid,t;
    while(cin>>n>>m){
        for (i=0;i<n;i++){
            cin>>an[i];
            if(i){
                if(left<an[i]) left = an[i];
            }else{
                left = an[i];
            }
            right += an[i];
        }
        while (left<right){
            mid = (left+right)/2;
            sum = 0;t = 0;
            for (i=0;i<n;i++){
                if (sum+an[i]>mid){//如果大于mid则区间短+1
                    sum = an[i];
                    t++;
                }
                else {
                    sum += an[i];
                }
            }
            if (t<m){//t<m,说明m取大了
                right = mid;
            }
            else{
                left = mid+1;
            }
        }
        cout<<right<<endl;
    }
    return 0;
}