[bzoj]4590: [Shoi2015]自动刷题机

二分答案，暴力验证。找到一个最小满足的值与一个最大满足的值。

记得最后判断二分的是否正确。

#include <cstdio>#include <algorithm>#define ll long longusing namespace std;int n,k;ll w[100005];ll sum,x,y;inline ll pd(ll x){register int i;ll now=0,ret=0;for (i=1;i<=n;i++){now+=w[i];if (now<0) now=0;if (now>=x) ret++,now=0;}return ret;}inline ll efmi(ll l,ll r){ll mid,ret=0;while (l<=r){mid=(l+r)>>1;if (pd(mid)<=k) r=mid-1,ret=mid;else l=mid+1;}return ret;}inline ll efma(ll l,ll r){ll mid,ret=0;while (l<=r){mid=(l+r)>>1;if (pd(mid)>=k) l=mid+1,ret=mid;else r=mid-1;}return ret;}int main(){register int i,j;scanf("%d %d",&n,&k);for (i=1;i<=n;i++){scanf("%lld",&w[i]);sum+=abs(w[i]);}x=efmi(1,sum);y=efma(1,sum);if (pd(x)!=k||pd(y)!=k) printf("-1");else printf("%lld %lld",x,y);return 0;}