2020.10.17天梯赛练习 和 16 号个人赛 补题报告

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7-9 小字辈 (25分)

题目链接:https://pintia.cn/problem-sets/1316714145967362048/problems/1316715025278029824

思路：就是深度优先搜索，访问的时候标记一下。做到O(n)的时间复杂度。

 

#include <iostream>
#include <cstdio>
#include <algorithm> 

using namespace std;
typedef long long ll;
const int N = 100010;

bool cmp(int a, int b){
	return a > b;
}

int parent[N], len[N];

int fun(int i){
	
    if(parent[i] == -1){
		len[i] = 1;
		return 1;
	}
	if(len[parent[i]] >= 1){
		len[i] = len[parent[i]] + 1;
		return len[i];
	}
    
	len[i] = fun(parent[i]) + 1;
	return len[i];
}

int main()
{
	int n;
	scanf("%d", &n);
	int res = 0;
	
	for(int i = 1;i <= n; ++ i){
		parent[i] = i;
	}
	for(int i = 1;i <= n; ++ i){
		int x;
		scanf("%d", &x);
		parent[i] = x;
	}
	
	for(int i = 1;i <= n; ++ i){
		fun(i);
		res = max(len[i], res);
	}
	
	printf("%d\n", res);
	int cnt = 0;
	for(int i = 1; i <= n; ++ i){
		if(res == len[i] && !cnt) printf("%d", i), cnt ++;
		else if(res == len[i] && cnt)  printf(" %d", i) , cnt ++;
	}
}

　

Power Sequence

原题链接：https://codeforces.com/problemset/problem/1397/B

思路：暴力求解...

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
const int N = 100010;

ll Pow(ll a, ll b){
	ll res = 1;
	
	for(int i = 1;i <= b; ++ i){
		res *= a;
	}
	
	return res;
} 

bool cmp(int a, int b){
	return a > b;
}

int a[N];
ll ans;
int main()
{
	
//	cout << Pow(2, 5);
	int n;
	scanf("%d", &n);
	
	for(int i = 1;i <= n; ++ i){
		scanf("%d", &a[i]);
		ans += abs(a[i] - 1);
	}
	
	if(n > 62){
		printf("%lld\n", ans);
		return 0;
	}
	sort(a + 1,a + 1 + n);
	ll res = ans;
	
	for(ll i = 1;i <= 1e6;i ++){
		if(Pow(i, n - 1) > 1e15 || Pow(i, n - 1) < 0) break;
		ans = abs(a[1] - 1);
		for(ll j = 2;j <= n; ++ j){
			ll tmp = Pow(i, j - 1); 
			ans += abs(a[j] - tmp);
		}
		res = min(ans, res);
	}
	
	printf("%lld\n",res);
}

　　

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