poj3273 Monthly Expense（二分搜索）

https://vjudge.net/problem/POJ-3273

认真审题，代码仔细！！ans的初值应该是1

 #include<iostream>
 #include<cstdio>
 #include<queue>
 #include<cstring>
 #include<algorithm>
 #include<cmath>
 #include<map>
 #define lson l, m, rt<<1
 #define rson m+1, r, rt<<1|1
 #define INF 0x3f3f3f3f
 typedef unsigned long long ll;
 using namespace std;
 ll n, m, a[];
 ll C(ll x)
 {
     ll ans=, sum=;//认真审题啊！！ans的初值是1
     for(int i = ; i < n; i++){
         sum += a[i];
         if(sum > x){
             if(a[i]>x) return ;//单个就>
             sum = a[i];
             ans++;
         }
         if(ans>m){
             return ;
         }
     }
     return ;
 }
 int main()
 {
     while(cin >> n >> m){
         for(int i = ; i < n; i++){
             cin >> a[i];
         }
         ll lb = , ub = INF;
         while(ub-lb>){
             ll mid = (lb+ub)>>;
             if(C(mid)){
                 ub = mid;
             }
             else{
                 lb = mid;
             }
         }
         cout << ub << endl;
     }
     return ;
 }