愤怒的牛

Posted 2021-01-05 lcan

 

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<algorithm>
 4 using namespace std;
 5 const int maxn=1e5+7;
 6 int n,m;
 7 int l,r,mid;
 8 int xx[maxn];
 9 bool check(int u){
10     int cnt=1;int lft=xx[1]+u;
11     for(int i=2;i<=n;i++){
12         if(lft<=xx[i]) {cnt++;lft=xx[i]+u;}
13     }
14     return cnt>=m;
15 }
16 int main(){
17     cin>>n>>m;
18     for(int i=1;i<=n;i++) cin>>xx[i];
19     sort(xx+1,xx+n+1);
20     l=0;r=xx[n]-xx[1];
21     while(l<=r){
22         mid=(l+r)/2;
23         if(check(mid)) l=mid+1;
24         else r=mid-1; 
25     }
26     cout<<r<<endl;
27     return 0;
28 }

如果不是l=mid+1,r=mid-1的话，因为这里都是整数，很可能出现l=mid的情况，这是就会无限循环下去

 

数列分段II

 1 #include<iostream>
 2 #include<cstdio>
 3 using namespace std;
 4 typedef long long ll;
 5 const ll maxn=1e6+7;
 6 ll n,m,l,r,mid;
 7 ll a[maxn];
 8 bool check(ll x){
 9     ll cnt=1;ll lft=a[1];
10     for(ll i=2;i<=n;i++){
11         if(lft+a[i]>x){cnt++;lft=a[i];}
12         else{lft+=a[i];}
13     }
14     return cnt<=m;
15 }
16 int main(){
17     cin>>n>>m;
18     for(ll i=1;i<=n;i++) {cin>>a[i];r+=a[i];l=max(l,a[i]);}
19     while(l<=r){
20         mid=(l+r)/2;
21         if(check(mid)) r=mid-1;
22         else l=mid+1;
23     }
24     cout<<l<<endl;
25     return 0;
26 }

l不能设成0