ACM-ICPC 2017 沈阳赛区现场赛 G. Infinite Fraction Path && HDU 6223（BFS）

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=6223

参考题解：https://blog.csdn.net/qq_40482495/article/details/78492841

注意优先队列自定义比较级的用法！！

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define mst(a,b) memset((a),(b),sizeof(a))
#define mp(a,b) make_pair(a,b)
#define pi acos(-1)
#define pii pair<int,int>
#define pb push_back
const int INF = 0x3f3f3f3f;
const double eps = 1e-6;
const int MAXN = 15e4 + 10;
const int MAXM = 2e6 + 10;

char s[MAXN];
int a[MAXN], ans[MAXN], vis[MAXN], nex[MAXN];

struct node {
    int pos,val,dep;
};

struct cmp {
    bool operator()(const node &x,const node &y) {
        if(x.dep != y.dep) return x.dep > y.dep;
        else if(x.val != y.val) return x.val < y.val;
        return x.pos < y.pos;
    }
};

int main() {
#ifdef local
    freopen("data.txt", "r", stdin);
#endif
    int cas = 1;
    int t;
    scanf("%d",&t);
    while(t--) {
        int n;
        scanf("%d",&n);
        scanf("%s",s);
        int mx = 0;
        for(int i = 0; i < n; i++) {
            ans[i] = vis[i] = -1;
            a[i] = s[i] - '0';
            mx = max(mx, a[i]);
            nex[i] = (1ll * i * i + 1) % n;
        }
        priority_queue<node, vector<node>, cmp >q;
        for(int i = 0; i < n; i++)
            if(a[i] == mx) q.push({i,a[i],0});
        while(!q.empty()) {
            node now = q.top();
            q.pop();
            int pos = now.pos, val = now.val, dep = now.dep;
            if(dep >= n) break;
            if(ans[dep] > val) continue;
            else if(ans[dep] == val && vis[pos] == dep) continue;
            ans[dep] = val, vis[pos] = dep;
            q.push({nex[pos],a[nex[pos]],dep + 1});
        }
        printf("Case #%d: ",cas++);
        for(int i = 0; i < n; i++) printf("%d",ans[i]);
        printf("
");
    }
    return 0;
}