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

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<queue>
 4 #include<cstring>
 5 #include<algorithm>
 6 #include<cmath>
 7 #include<map>
 8 #define lson l, m, rt<<1
 9 #define rson m+1, r, rt<<1|1
10 #define INF 0x3f3f3f3f
11 typedef unsigned long long ll;
12 using namespace std;
13 ll n, m, a[100010];
14 ll C(ll x)
15 {
16     ll ans=1, sum=0;//认真审题啊！！ans的初值是1 
17     for(int i = 0; i < n; i++){
18         sum += a[i];
19         if(sum > x){
20             if(a[i]>x) return 0;//单个就> 
21             sum = a[i];
22             ans++;
23         }
24         if(ans>m){
25             return 0;
26         }
27     }
28     return 1;
29 }
30 int main()
31 {
32     while(cin >> n >> m){
33         for(int i = 0; i < n; i++){
34             cin >> a[i];
35         } 
36         ll lb = 0, ub = INF; 
37         while(ub-lb>1){
38             ll mid = (lb+ub)>>1;
39             if(C(mid)){
40                 ub = mid;
41             }
42             else{
43                 lb = mid;
44             } 
45         }
46         cout << ub << endl;        
47     } 
48     return 0;
49 }