P1182 数列分段 Section II

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#include<bits/stdc++.h>
using namespace std;

typedef long long LL;
const int N=1e5+10;
int n,m;
int a[N];

bool check(int x)
{
    int cnt=1;
    LL sum=0;
    for(int i=1;i<=n;i++){
        if(sum+a[i]>x){
            sum=a[i];
            cnt++;
        }else{
            sum+=a[i];
        }
    }

    return cnt<=m;
}

int main()
{
    ios::sync_with_stdio(0),cin.tie(0);
    cin>>n>>m;

    int l=0;
    LL r=0;
    for(int i=1;i<=n;i++){
        cin>>a[i];
        l=max(a[i],l);
        r+=a[i];
    }

    int ans=0;
    while(l<=r){
        int mid=l+(r-l)/2;
        if(check(mid)){
            r=mid-1;
            ans=mid;
        }else{
            l=mid+1;
        }
    }

    cout<<ans<<endl;
}