ACM multi-school season training Luo Guchun

T122399 Goldbach's conjecture

Meaning of the questions: give you n, let your card Goldbach conjecture, 1e9 complexity;

This question of how complicated calculation is not right, not a linear array that big screen,
and then surprised the violence actually passed.
Proof follows:

 

 log (n) too soon Yeah, about 1e9 also 30, so count on the right;

#include<bits/stdc++.h>
using namespace std;
bool isprime(int x){
    for(int i=2;i*i<=x;i++){
    if(x%i==0)return 0;
    }
    return 1;
}
int main(){
    int n;
    cin>>n;
    for(int i=2;i*i<n;i++){
    if(isprime(i)&&isprime(n-i)){
    cout<<i<<" "<<n-i<<endl;
    break;
    }
    }


    return 0;
}

View Code

T122397 Everybody deserves a long long name

This problem is not level;

Do not say;

T122394 Billionaire

Meaning of the questions: is to ask how many days you can become a billionaire, output date.

Solution: separation of two days, and then by seeking the date zeller formula;

I'm stuck here for a while, is two points, the biggest blind zone is not selected, think also understand that I started to get a lot, he would skip the correct answer,

Therefore, if r sqrt (2e9), solving the equation to obtain;

Although half fast, but you can not choose a large range, otherwise the answer is not right, L small, R big, will skip the correct answer,

#include<bits/stdc++.h>
using namespace std;
int getId(int y, int m, int d) {
    if (m < 3) {y --; m += 12;}
    return 365 * y + y / 4 - y / 100 + y / 400 + (153 * (m - 3) + 2) / 5 + d - 307;
}
vector<int> date(int id) {
    int x = id + 1789995, n, i, j, y, m, d;
    n = 4 * x / 146097;
    x -= (146097 * n + 3) / 4;
    i = (4000 * (x + 1)) / 1461001; x -= 1461 * i / 4 - 31;
    j = 80 * x / 2447; d = x - 2447 * j / 80; x = j / 11;
    m = j + 2 - 12 * x; y = 100 * (n - 49) + i + x;
    vector<int>v;
    v.push_back(y),v.push_back(m),v.push_back(d);
    return v;
}
int m;
const int maxn=1000000000;
bool check(int x){
    int sum=m+x*(x+1)/2;
    if(sum>=maxn)return 1;
    else return 0;
}
int main(){
    int t;
    cin>>t;
    while(t--){
    int ty,tm,td;
    scanf("%d %d %d %d",&m,&ty,&tm,&td);
    int id=getId(ty,tm,td);
    int l=0,r=sqrt(2e9);
    while(l<=r){
    int mid=(r+l)/2;
    if(check(mid))r=mid-1;
    else l=mid+1;
    }
    id+=l;
    vector<int>ans=date(id);
    printf("%d %d %d\n",ans[0],ans[1],ans[2]);
    }
    // system("pause");
    return 0;
}

View Code

 

T122398 Final Spark

This question about such a question:

 

 That is launching a light, and asked to be shot in the probability that you are. The person radius r, the radius of hop s, lightwave width w, the distance d,

Useless distance d, w + 2r problem is converted into the optical wave how inscribed circle, the maximum coverage area.

pending upgrade;