蓝桥杯练习题（五）

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本文主要是【算法】——蓝桥杯练习题（五）的文章，如果有什么需要改进的地方还请大佬指出⛺️

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2080.求和


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.StreamTokenizer;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub
		StreamTokenizer sc = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
		sc.nextToken();
		int n = (int)sc.nval;
		int a[] = new int[n];
		long sum[] = new long[n+1];
		for(int i=0;i<n;i++) {
			sc.nextToken();
			a[i] = (int)sc.nval;
		}
		sum[0]=a[0];
		for(int i=1;i<n;i++) {
			sum[i]=sum[i-1]+a[i];
		}
		long res = 0;
		for(int i=0;i<n;i++) {
			res+=a[i]*(sum[n-1]-sum[i]);
		}
		System.out.println(res);
	}

}

2145.求阶乘

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		long l = 1;
		long r = (long)9e18;
		while(l<r) {
			long mid = (r-l)/2+l;
			if(f(mid)>=n) {
				r = mid;
			}else {
				l = mid+1;
			}
		}
		if(f(l)==n) {
			System.out.println(l);
		}else {
			System.out.println(-1);
		}
	}
	
	public static long f(Long n) {
		long ans = 0;
		while(n>0) {
			ans+=n/5;
			n/=5;
		}
		return ans;
	}

}

2140.星期计算

import java.util.Scanner;
// 1:无需package
// 2: 类名必须Main, 不可修改

public class Main {
    	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int a = f(20, 22);
		System.out.println((a+6)%7==0?7:(a+6)%7);
	}
	
	public static int f(int a,int b) {
		int ans=1,t=a;
		for(int i=0;i<b;i++) {
			ans=a%7;
			a=ans*t;
		}
		return ans;
	}
}