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[100010];
ll C(ll x)
{
    ll ans=1, sum=0;//认真审题啊！！ans的初值是1 
    for(int i = 0; i < n; i++){
        sum += a[i];
        if(sum > x){
            if(a[i]>x) return 0;//单个就> 
            sum = a[i];
            ans++;
        }
        if(ans>m){
            return 0;
        }
    }
    return 1;
}
int main()
{
    while(cin >> n >> m){
        for(int i = 0; i < n; i++){
            cin >> a[i];
        } 
        ll lb = 0, ub = INF; 
        while(ub-lb>1){
            ll mid = (lb+ub)>>1;
            if(C(mid)){
                ub = mid;
            }
            else{
                lb = mid;
            } 
        }
        cout << ub << endl;        
    } 
    return 0;
}