L. Spicy Restaurant （多源bfs

L. Spicy Restaurant
思路：
枚举一个辣度 \(c\)，把所有 \(w_i=c\) 的点作为起点进行 \(bfs\)
预处理出 \(dis[j][i]\) 表示 \(i\) 点距离辣度 \(j\) 有多远
然后顺着更新一遍 \(dis[i][j] = min(dis[i][j-1], dis[i][j])\)
因为满足 \(a_j<=c\) 的辣度都是合法的
有点卡常，\(scanf\) 读入

点击查看代码

#include<bits/stdc++.h>
#define endl '\n'
#define ll long long
#define ull unsigned long long
#define ld long double
#define all(x) x.begin(), x.end()
#define mem(x, d) memset(x, d, sizeof(x))
#define eps 1e-6
using namespace std;
const int maxn = 1e5 + 9;
const int mod = 1e9 + 7;
const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3f;
ll n, m;
int q;
int dis[maxn][109];
int w[maxn];
vector <int> e[maxn];

void bfs(int c){
	queue <int> q;
	for(int i = 1; i <= n; ++i) if(w[i] == c) q.push(i), dis[i][c] = 0;
	while(!q.empty()){
		int x = q.front();q.pop();
		for(auto to : e[x]){
			if(dis[to][c] > dis[x][c] + 1){
				dis[to][c] = dis[x][c] + 1;
				q.push(to);
			}
		}
	}
}
void work()
{
	mem(dis, 0x3f);
	cin >> n >> m >> q;
	for(int i = 1; i <= n; ++i) scanf("%d", &w[i]);
	while(m--){
		int x, y;scanf("%d %d", &x, &y);
		e[x].push_back(y);e[y].push_back(x);
	}
	for(int i = 100; i >= 1; --i) bfs(i);
	for(int i = 1; i <= n; ++i)
		for(int j = 1; j <= 100; ++j)
			dis[i][j] = min(dis[i][j-1], dis[i][j]);
	while(q--){
		int l, r;scanf("%d %d", &l, &r);
		printf("%d\n", dis[l][r] == inf ? -1 : dis[l][r]);
	}
}

int main()
{
//	ios::sync_with_stdio(0);
//	int TT;cin>>TT;while(TT--)
	work();
	return 0;
}