A 梦想赛道

分析

在原树的基础上，选一条之前存在的边加一条边权为 $11$ 的边即可.

代码实现

#include <bits/stdc++.h>
using namespace std;

template <typename T>
inline void read(T& x)
{
    x = 0; int f = 1; char ch = getchar();
    while(!isdigit(ch)) {if(ch == '-') f = -1; ch = getchar();}
    while(isdigit(ch))  {x = x * 10 + ch - '0', ch = getchar();}
    x *= f;
}

template <typename T>
void print(T x)
{
    if(x < 0) putchar('-'), x = -x;
    if(x > 9) print(x / 10);
    putchar(x % 10 + '0');
}

template <typename T>
void print(T x, char ch)
{
    print(x), putchar(ch);
}

typedef double db;
typedef long long ll;

const int M = (int)1e5;
const int N = (int)1e5;
const int inf = 0x3f3f3f3f;
const ll mod = (ll)1e9 + 7;

void work()
{
    int n; read(n);
    int s = 0, mx = 0;
    for(int i = 2, u, v, w; i <= n; ++i)
    {
        read(u), read(v), read(w);
        s += w, mx = max(mx, w);
    }
    if(mx == 1) print(-1, '\n');
    else        print(s + 1, '\n');
}

int main()
{
//    ios::sync_with_stdio(0);
//    cin.tie(0); cout.tie(0);
//    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);
//    int T; read(T);
//    for(int ca = 1; ca <= T; ++ca)
//    {
//        work();
//    }
    work();
//    cerr << 1.0 * clock() / CLOCKS_PER_SEC << "\n";
    return 0;
}

B 寒冬信使

分析

从后往前模拟即可.

代码实现

#include <bits/stdc++.h>
using namespace std;

template <typename T>
inline void read(T& x)
{
    x = 0; int f = 1; char ch = getchar();
    while(!isdigit(ch)) {if(ch == '-') f = -1; ch = getchar();}
    while(isdigit(ch))  {x = x * 10 + ch - '0', ch = getchar();}
    x *= f;
}

template <typename T>
void print(T x)
{
    if(x < 0) putchar('-'), x = -x;
    if(x > 9) print(x / 10);
    putchar(x % 10 + '0');
}

template <typename T>
void print(T x, char ch)
{
    print(x), putchar(ch);
}

typedef double db;
typedef long long ll;

const int M = (int)1e5;
const int N = (int)1e5;
const int inf = 0x3f3f3f3f;
const ll mod = (ll)1e9 + 7;

char s[M + 5];

void work()
{
    scanf("%s", s + 1);
    int n = strlen(s + 1);
    int ans = 0;
    for(int i = n; i >= 1; --i)
    {
        if(s[i] == '1') ++ans, s[i - 1] ^= 1;
    }
    puts(!(ans & 1) ? "X" : "T");
}

int main()
{
//    ios::sync_with_stdio(0);
//    cin.tie(0); cout.tie(0);
//    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);
    int T; read(T);
    for(int ca = 1; ca <= T; ++ca)
    {
        work();
    }
//    work();
//    cerr << 1.0 * clock() / CLOCKS_PER_SEC << "\n";
    return 0;
}