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+" ");
		}
	}
}
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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));
		}
	}
}
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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();
	}
}
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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);
	}
}
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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 9
		int mid = res[n/2];
		int sum = 0;
		for(int i=0;i<n;i++) {
			sum+=Math.abs(mid-res[i]);
		}
		System.out.println(sum);
	}
}
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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();
		}
	}
}
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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));
		}
	}
}
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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true
		if(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n
		int 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
	}
}
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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();
	}
}
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