【每日一题】蓝桥杯历年真题题解 - 杨辉三角形 - 新鲜讯息

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今日「每日一题」来啦！历年真题题目：杨辉三角形。还没有加入专属刷题群的小伙伴，记得扫码哟～（每天会在群里发蓝桥杯历年真题）

题目描述

解题思路

参考代码

1、C/C++组

#include<bits/stdc++.h>#define int long longusing namespace std;int n;int C(int a , int b){    int res = 1;    for(int i = a , j = 1 ; j <= b ; i -- , j ++){        res = res * i / j;        if(res > n) return res;    }    return res;}signed main(){    cin >> n;    for(int k = 16 ; ~k ; k --){        int l = 2 * k , r = max(n , l) , res = -1;        while(l <= r){            int mid = l + r >> 1;            if(C(mid , k) >= n) res = mid , r = mid - 1;            else l = mid + 1;        }        if(C(res , k) == n) return cout << (res + 1) * res / 2 + k + 1 << 'n' , 0;    }    return 0;}

2、Java组

import java.util.*;
public class Main {    private static int n;
    private static long C(long a, long b) {        long res = 1;        for (long i = a, j = 1; j <= b; i--, j++) {            res = res * i / j;            if (res > n) {                return res;            }        }        return res;    }
    public static void main(String[] args) {        Scanner cin = new Scanner(System.in);        n = cin.nextInt();        for (int k = 16; k >= 0; k--) {            int l = 2 * k, r = Math.max(n, l), res = -1;            while (l <= r) {                int mid = l + r >> 1;                if (C(mid, k) >= n) {                    res = mid;                    r = mid - 1;                } else {                    l = mid + 1;                }            }            if (C(res, k) == n) {                System.out.println((long) (res + 1) * res / 2 + k + 1);                break;            }        }        cin.close();    }}

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3、Python组

import osimport sys
n = int(input())

def C(a, b):    res = 1    i = a    j = 1    while j <= b:        res = int(res * i / j)        if res > n:            return int(res)        i -= 1        j += 1    return int(res)

for k in range(16, -1, -1):    l = 2 * k    r = max(n, l)    res = int(-1)    while l <= r:        mid = l + r >> 1        if C(mid, k) >= n:            res = mid            r = mid - 1        else:            l = mid + 1    if C(res, k) == n:        print((res + 1) * res // 2 + k + 1)        break