学步园

这好像是做的第一道二分，当时完全没思路，参考别人代码以后豁然开朗！

#include <iostream>
#include <fstream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <vector>
#include <bitset>
#include <cmath>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <ctime>
#define LL long long
#define Vi vector<int>
#define Si set<int>
#define readf freopen("input.txt","r",stdin)
#define writef freopen("output.txt","w",stdout)
#define FU(i,a) for(int i(1); i <= (a); i++)
#define FD(i,a) for(int i(a); i >= (1); i--)
#define FOR(i,a,b) for(int i(a);i <= (b); i++)
#define FORD(i,a,b) for(int i(a);i >= (b); i--)
#define SET(a,b) memset(a,b,sizeof(a))
#define SD(a) scanf("%d",&(a))
#define LN printf("\n")
#define PS printf(" ")
#define pb push_back
using namespace std;
const int maxn=3000;
int n,m,a[100001];
int low,high,mid;
int solve(int k)
{
    int sum=a[1];
    int group=1;
    FOR(i,2,n)
    {
        if(sum+a[i]<=k)
            sum+=a[i];
        else
        {
            sum=a[i];
            group++;
            if(group>m)
                return 1;// 1代表mid太小
        }
    }
    return -1;//mid 太大
}
int main()
{
    SD(n);SD(m);
    FOR(i,1,n){
        SD(a[i]);
        high+=a[i];
        if(low<a[i])
            low=a[i];
    }
    mid=(low+high)/2;
    while(low<high)
    {
        int t=solve(mid);
        if(t==1) //mid is low
        {
            low=mid+1;
        }
        else
        {
            high=mid-1;
        }
        mid=(low+high)/2;
    }
    printf("%d\n",mid);
    return 0;
}