ybtoj：二分算法
A：数列分段
点击查看代码
#include<bits/stdc++.h>
using namespace std;
int m,n;
int a[100002];
int l,r;
bool check(int limit){
int cnt=1,sum=0;
for(int i=1;i<=n;i++)
{
if(sum+a[i]>limit){
cnt++;
sum=a[i];
}
else{
sum+=a[i];
}
}
return cnt<=m;
}
int main()
{
cin>>n>>m;
for(int i=1;i<=n;i++)
{
cin>>a[i];
r+=a[i];
if(a[i]>l)
{
l=a[i];
}
}
while(l<r)
{
int mid=(l+r)>>1;
if(check(mid)==1)
{
r=mid;
}
else{
l=mid+1;
}
}
cout<<l;
return 0;
}
B：防具布置
点击查看代码
#include<bits/stdc++.h>
using namespace std;
#define int long long
const int N=2e5+15;
int t;
int n;
int s[N], e[N], d[N];
int num(int k) {
int ans = 0;
for (int ii = 1; ii <= n; ii++) {
if (s[ii] <= k)ans += (min(k, e[ii]) - s[ii] / d[ii] + 1);
}
return ans;
}
void work() {
scanf("%lld",&n);
for (int i = 1; i <= n; i++) {
scanf("%lld%lld%lld", &s[i], &e[i], &d[i]);
}
//cout<<r<<endl;
if (num(2147483649) % 2 == 0) {
printf("There's no weakness.\n");
//cout << "" << endl;
return;
}
int l = 0, r = 2147483647;
while (l < r) {
int mid = (long long)(l + r) >> 1;
if (num(mid) & 1) {
r = mid;
} else {
l = mid + 1;
}
}
printf("%lld %lld\n",l,num(l)-num(l-1));
//cout << l << " " << num(l) - num(l - 1) << endl;
}
signed main() {
cin >> t;
while (t--) {
work();
}
return 0;
}
C：最大均值
点击查看代码
#include<bits/stdc++.h>
using namespace std;
const int N=100005;
int n,l;
double a[N],qzh[N],b[N];
const double e=1e-5;
bool check(double num){
for(int i=1;i<=n;i++) b[i]=a[i]-num;
for(int i=1;i<=n;i++) qzh[i]=qzh[i-1]+b[i];
double minn=1e8;
double ans=-1e8;
for(int i=l;i<=n;i++){
minn=min(minn,qzh[i-l]);
ans=max(ans,qzh[i]-minn);
}
return ans>=0;
}
int main(){
scanf("%d%d",&n,&l);
for(int i=1;i<=n;i++){
scanf("%lf",&a[i]);
}
double l=-1e6,r=1e6;
while(l+e<r){
double mid=(l+r)/2;
if(check(mid)){
l=mid;
}
else {
r=mid;
}
}
cout<<int(r*1000)<<endl;
return 0;
}
D：喂养宠物
点击查看代码
#include<bits/stdc++.h>
using namespace std;
const int N=55;
int hun[N],grd[N];
int n,tot;
bool rabbit(int x){
int re[N];
for(int i=1;i<=n;i++)re[i]=hun[i]+(x-1)*grd[i];
sort(re+1,re+n+1);
int ans=0;
for(int i=1;i<=x;i++){
ans+=re[i];
}
return ans<=tot;
}
int main(){
scanf("%d%d",&n,&tot);
for(int i=1;i<=n;i++)scanf("%d",&hun[i]);
for(int j=1;j<=n;j++)scanf("%d",&grd[j]);
int l=1,r=n;
while(l<r){
int mid=(l+r)/2;
if(rabbit(mid)) l=mid+1;
else r=mid;
}
cout<<l-1<<endl;
return 0;
}
E：最小时间
点击查看代码
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=1e6+10;
int n,m;
ll s;
int k[N],b[N];
ll val[N];
bool check(int x){
for(int i=1;i<=n;i++){
val[i]=1ll*k[i]*x + b[i];
}
nth_element(val+1,val+m,val+n+1,greater<ll>());
ll sum=0;
for(int i=1;i<=m;i++){
if(val[i]>0 && (sum+=val[i])>=s){
return true;
}
}
return sum>=s;
}
int main(){
scanf("%d%d%lld",&n,&m,&s);
for(int i=1;i<=n;i++){
scanf("%d%d",&k[i],&b[i]);
}
if(check(0)){
cout<<0;
return 0;
}
int l=1,r=1e9+1;
while(l<r){
int mid=(l+r)/2;
if(check(mid)) r=mid;
else l=mid+1;
}
printf("%d\n",l);
return 0;
}
F：攻击法坛
点击查看代码
#include<bits/stdc++.h>
#define int long long
using namespace std;
int n,R,G;
const int N=2024;
int a[N],p[N],q[N],dp[N][N];
int ans;
inline bool check(int l){
memset(dp,0,sizeof(dp));
memset(p,0,sizeof(p));
memset(q,0,sizeof(q));
for(int i=1;i<=n;i++){
for(int j=i;j<=n;j++){
if(a[j]-a[i]+1<=l){
p[i]=j;
}
if(a[j]-a[i]+1<=2*l){
q[i]=j;
}
}
}
p[n+1]=q[n+1]=n;
for(int i=0;i<=R;i++){
for(int j=0;j<=G;j++){
if(i>0){
dp[i][j]=max(dp[i][j],p[dp[i-1][j]+1]);
}
if(j>0){
dp[i][j]=max(dp[i][j],q[dp[i][j-1]+1]);
}
}
}
return dp[R][G]==n;
}
signed main(){
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin>>n>>R>>G;
for(int i=1;i<=n;i++){
cin>>a[i];
}
sort(a+1,a+n+1);
int l=1,r=a[n]-a[1]+1;
if(R+G>=n){
cout<<"1\n";
return 0;
}
while(l<=r){
int mid=l+r>>1;
if(check(mid)){
r=mid-1;ans=mid;
}
else {
l=mid+1;
}
}
cout<<ans<<"\n";
return 0;
}
G：跳石头
点击查看代码
#include<bits/stdc++.h>
using namespace std;
const int N=5e4+10;
int l,n,m;
int dis[N];
inline bool nb(int x){
int sum=0,cnt=0;
for(int i=1;i<=n;i++){
if(dis[i]-sum<x) cnt++;
else sum=dis[i];
}
if(l-sum<x) cnt++;
return cnt<=m;
}
int main(){
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin>>l>>n>>m;
for(int i=1;i<=n;i++){
cin>>dis[i];
}
int ll=0,rr=l;
while(ll<rr){
int mid=(ll+rr+1)/2;
if(nb(mid))ll=mid;
else rr=mid-1;
}
cout<<ll;
return 0;
}
H：飞离地球
点击查看代码
#include<bits/stdc++.h>
using namespace std;
const int N=114514,M=1919810;
int n,m,cnt,t;
int l=-1e5,r=1e5;
long long ans;
struct edge{
int w,to,nxt;
}e[M*2];
int u[N],v[N],w[N],head[N],dis[N],cis[N];
bool vis[N],arrive[N];
inline int read(){
int cxk=0,f=1;
char c=getchar();
while(c<'0' || c>'9'){
if(c=='-') f=-f;
c=getchar();
}
while(c>='0' && c<='9'){
cxk=(cxk<<3)+(cxk<<1)+c-'0';
c=getchar();
}
return cxk*f;
}
inline void add(int u,int v,int w){
e[++cnt].w=w;
e[cnt].to=v;
e[cnt].nxt=head[u];
head[u]=cnt;
}
inline void dfs(int u){
arrive[u]=1;
for(int i=head[u];i;i=e[i].nxt){
int t=e[i].to;
if(!arrive[t]) dfs(t);
}
}
inline int spfa(int x){
queue<int> q;
memset(dis,0x3f3f3f3f,sizeof(dis));
memset(vis,0,sizeof(vis));
memset(cis,0,sizeof(cis));
q.push(1);
vis[1]=1,dis[1]=0,cis[1]=1;
while(!q.empty()){
int k=q.front();
q.pop();
vis[k]=0;
for(int i=head[k];i;i=e[i].nxt){
int t=e[i].to;
if(!arrive[t]) continue;
if(dis[k]+e[i].w+x<dis[t]){
dis[t]=dis[k]+e[i].w+x;
if(!vis[t]){
vis[t]=1;
cis[t]=cis[k]+1;
if(cis[t]>n) return -1;
q.push(t);
}
}
}
}
return dis[n];
}
int main(){
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
t=read();
while(t--){
memset(arrive,0,sizeof(arrive));
memset(head,0,sizeof(head));
cnt=0;
n=read(),m=read();
for(int i=1;i<=m;i++){
u[i]=read(),v[i]=read(),w[i]=read();
add(v[i],u[i],w[i]);
}
dfs(n);
if(!arrive[1]){
cout<<"-1\n";
continue;
}
memset(head,0,sizeof(head));
cnt=0;
for(int i=1;i<=m;i++) add(u[i],v[i],w[i]);
l=-1e5,r=1e5;
while(l<r){
int mid=l+r>>1;
long long val=spfa(mid);
if(val>=0){
r=mid;
ans=val;
}
else l=mid+1;
}
cout<<ans<<"\n";
}
return 0;
}
//抄袭绝非良策，理解才是正道
浙公网安备 33010602011771号