题解

服了两个WA害我耗费宝贵的一天一次获取测试点机会
还硬控我十分钟

#include <iostream>
#include <cstdio>
#define int long long
using namespace std;
int a[100005];
int n, m, ct;
bool check(int x){//正常check函数，用贪心求当最大值为x时最小分段数
	int ct = 1, ctt = 0;
	for(int i = 1; i <= n; i++){
		if(a[i] > x) return 0;//注意如果a[i]>x说明不可能有这样的分段，返回0
		ctt += a[i];
		if(ctt > x){
			ct++;
			ctt = a[i];
		}
	}
	return ct <= m;
}
signed main(){
	cin >> n >> m;
	for(int i = 1; i <= n; i++){
		cin >> a[i];
		ct += a[i];
	}int left = 1, right = ct;
	while(left <= right){//二分模版
		int mid = (left + right) / 2;
		if(check(mid)) right = mid - 1;
		else left = mid + 1;
	}cout << left;

	return 0;
}

时间复杂度：$O(nlog_2sum(a))$