Educational Codeforces Round 103 [Rated for Div. 2]补题

C

C. Longest Simple Cycle

题意

给出一个由n条链连接成的图，求出最长的循环圈的长度。其中ci表示第i条链的顶点个数，ai和bi表示第i条链起点和终点所连接的上一条链的点的编号。

思路

对于i+2->i+3链组成的环，分两种情况

1. 如果a[i] != b[i]将前面的i+1->i+2链组成的环，合并进来
2. i+2->i+3链组成的环自己闭合

在枚举中分别考虑这两种情况并且取最大值即可保证最后的答案是最优解。

代码

/*************************************************************************
 > FileName:
 > Author:      Lance
 > Mail:        lancelot_hcs@qq.com
 > Date:        9102.1.8
 > Description:
 ************************************************************************/
//#include <bits/stdc++.h>
//#pragma comment(linker, "/STACK:102400000,102400000")//add_stack
#include <algorithm>
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <vector>
#include <cstdio>
#include <bitset>
#include <string>
#include <cmath>
#include <deque>
#include <queue>
#include <stack>
#include <map>
#include <set>
using namespace std;
typedef long long ll;
typedef pair<int, int> PII;
const double pi = acos(-1.0);
const double eps = 1e-6;
const int mod = 1e9 + 7;
#define debug(a) cout << "*" << a << "*" << endl
const int INF = 0x3f3f3f3f;//int2147483647//ll9e18//unsigned ll 1e19
const int maxn = 1000005;
//sacnf("%lf") printf("%f")
ll read()
{
    ll x = 0,f = 1;
    char ch = getchar();
    while (ch < '0' || ch > '9')
	{
		if (ch == '-')
		f = -1;
		ch = getchar();
	}
    while (ch >= '0' && ch <= '9')
	{
		x = x * 10 + ch - '0';
		ch = getchar();
	}
    return x * f;
}
ll t, n;
ll a[maxn], b[maxn], c[maxn], ans = 0;
void solve()
{
	t = read();
	while (t--) {
		n = read();
		ans = 0;
		for (int i = 0; i < n; i++) {
			c[i] = read();
		}
		for (int i = 0; i < n; i++) {
			a[i] = read();
		}
		for (int i = 0; i < n; i++) {
			b[i] = read();
		}
		ll tmp = 0;
		for (int i = 1; i < n; i++) {
			if (i == 1) {
				// self
				// +before
				tmp += abs(a[i] - b[i]) + 1 + c[i];
			} else {
				if (a[i] != b[i]) {
					tmp = max(abs(a[i] - b[i]) + 1 + c[i], tmp + c[i] -  abs(a[i] - b[i]) + 1);
				} else {
					tmp = abs(a[i] - b[i]) + 1 + c[i];
				}
			}
			ans = max(ans, tmp);
		}
		cout << ans << endl;
	}
}

int main()
{

//    freopen("F:/Overflow/in.txt","r",stdin);
//    ios::sync_with_stdio(false);
    solve();
    return 0;
}

小结

被hacked了呜呜呜

参考

https://www.cnblogs.com/KeepInCode/p/14348489.html