蓝桥杯（3.12）

1064: 【模板】埃氏筛法

import java.util.Scanner;public class Main{static final int N = 2000010;static boolean[] vis = new boolean[N];public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();vis[0] = true;vis[1] = true;for(int i=2;i<=n;i++) {if(!vis[i]) {for(int j=2*i;j<=n;j+=i)vis[j] = true;}}for(int i=2;i<=n;i++) {if(!vis[i])System.out.print(i+" ");}}
}

1051: 【模板】gcd和lcm

import java.util.Scanner;public class Test03{public static long gcd(long a,long b) {return b == 0 ? a : gcd(b,a%b);}public static long lcm(long a,long b) {return (a*b)/gcd(a,b);}public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();while(n-- != 0) {long a = sc.nextLong();long b = sc.nextLong();System.out.println(gcd(a,b)+" "+lcm(a,b));}}
}

1047: 【模板】快速幂

import java.util.Scanner;public class Main {static long qmi(long a, long b, long c) {long res = 1;while (b != 0) {if ((b & 1) == 1) {res = res * a % c;}a = a * a % c;b >>= 1;}return res;}static void solve() {Scanner scanner = new Scanner(System.in);int t = scanner.nextInt();while (t-- != 0) {int a = scanner.nextInt();int b = scanner.nextInt();int c = scanner.nextInt();System.out.println(qmi(a, b, c));}}public static void main(String[] args) {solve();}
}

a的b次幂mod c

1055. 股票买卖 II

import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();int[] res = new int[n+1];int sum = 0;for(int i=1;i<=n;i++) {res[i] = sc.nextInt();if(i>=2) {if(res[i]>res[i-1]) {sum+=res[i]-res[i-1];}}}System.out.println(sum);}
}

104. 货仓选址

import java.util.Arrays;
import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();int[] res = new int[n];for(int i=0;i<n;i++) {res[i] = sc.nextInt();}Arrays.sort(res);//1 2 6 9int mid = res[n/2];int sum = 0;for(int i=0;i<n;i++) {sum+=Math.abs(mid-res[i]);}System.out.println(sum);}
}

矩阵相乘

import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();int m = sc.nextInt();int k = sc.nextInt();int[][] a = new int[n][m];int[][] b = new int[m][k];int[][] c = new int[n][k];for(int i=0;i<n;i++) {for(int j=0;j<m;j++) {a[i][j] = sc.nextInt();}}for(int i=0;i<m;i++) {for(int j=0;j<k;j++) {b[i][j] = sc.nextInt();}}for(int i=0;i<n;i++) {for(int j=0;j<k;j++) {for(int z=0;z<m;z++) {c[i][j] += a[i][z]*b[z][j];}System.out.print(c[i][j]+" ");}System.out.println();}}
}

最大公约数

import java.util.Scanner;public class Main {public static int gcd(int a,int b) {return b == 0 ? a : gcd(b,a%b);}public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();while(n-- != 0) {int a = sc.nextInt();int b = sc.nextInt();System.out.println(gcd(a,b));}}
}

疑似素数

import java.util.Scanner;public class Main {public static boolean isTrue(int i) {int num = 0;int n = i;//保存i的初始值while(n!=0) {int t = n%10;num+=t;n/=10;}//如果每一位求和得到的数是质数就返回trueif(num < 2)return false;for(int j=2;j<=num/j;j++) {if(num % j == 0)return false;}return true;}public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();//输入nint sum = 0;//记录满足条件的数目for(int i=2;i<=n;i++) {//2 3 5 7 if(isTrue(i)) {sum++;}}System.out.println(sum);//输出结果}
}

小明的素数对

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;public class Main {static final int N = 100010;static boolean[] vis = new boolean[N];static BufferedReader br = new  BufferedReader(new InputStreamReader(System.in));static PrintWriter pw = new PrintWriter(new OutputStreamWriter(System.out));public static void main(String[] args) throws IOException{int n = Integer.parseInt(br.readLine());vis[0] = true;vis[1] = true;for(int i=2;i<=n;i++) {if(!vis[i]) {for(int j=2*i;j<=n;j+=i) {vis[j] = true;}}}List<Integer> list = new ArrayList<>();for(int i=2;i<=n;i++) {if(!vis[i]) {list.add(i);}}int sum = 0;for(int i=0;i<list.size();i++) {for(int j=i+1;j<list.size();j++) {int k = list.get(j) - list.get(i);if((!vis[k])) {sum++;}}}pw.println(sum);pw.close();}
}