CF 567D(One-Dimensional Battle Ships-二分)
裸二分
#include<cstdio> #include<cstring> #include<cstdlib> #include<algorithm> #include<functional> #include<iostream> #include<cmath> #include<cctype> #include<ctime> using namespace std; #define For(i,n) for(int i=1;i<=n;i++) #define Fork(i,k,n) for(int i=k;i<=n;i++) #define Rep(i,n) for(int i=0;i<n;i++) #define ForD(i,n) for(int i=n;i;i--) #define RepD(i,n) for(int i=n;i>=0;i--) #define Forp(x) for(int p=pre[x];p;p=next[p]) #define Forpiter(x) for(int &p=iter[x];p;p=next[p]) #define Lson (x<<1) #define Rson ((x<<1)+1) #define MEM(a) memset(a,0,sizeof(a)); #define MEMI(a) memset(a,127,sizeof(a)); #define MEMi(a) memset(a,128,sizeof(a)); #define INF (2139062143) #define F (100000007) #define MAXN (200000+10) typedef long long ll; ll mul(ll a,ll b){return (a*b)%F;} ll add(ll a,ll b){return (a+b)%F;} ll sub(ll a,ll b){return (a-b+(a-b)/F*F+F)%F;} void upd(ll &a,ll b){a=(a%F+b%F)%F;} int n,k,a,m; int x[MAXN],x2[MAXN]; bool check(int m) { For(i,m) x2[i]=x[i]; sort(x2+1,x2+1+m); int l=1,tot=0; For(i,m) { int len=x2[i]-l+1; tot+=len/(a+1); l=x2[i]+1; } tot+=(n+1-l+1)/(a+1); if (tot>=k) return 1; return 0; } int main() { // freopen("D.in","r",stdin); // freopen(".out","w",stdout); cin>>n>>k>>a>>m; For(i,m) scanf("%d",&x[i]); int l=1,r=m,ans=INF; while(l<=r) { int m=(r+l)/2; if (check(m)) l=m+1; else r=m-1,ans=min(ans,m); } if (ans==INF) ans=-1; cout<<ans<<endl; return 0; }