RT，小蒟蒻在写代码的时候遇到了下面这种神奇情况：

• GCC : 正常运行
• GCC -O2 : RE
• Clang++ : 正常运行
• Clang++ -O2 : 正常运行

我认为可能是有 UB，但是我太菜了，找了半天没找出来。

下面附代码（std = C++14）

#include <bits/stdc++.h>
#include <bits/extc++.h>

#define MAXN 5505
#define INF 0x3f3f3f3f
#define P 51

struct pr {
    int first, second;
    pr(int a, int b) : first(a), second(b) {}
    pr() {}
    bool operator > (const pr& x) const {
        return second > x.second;
    }
    bool operator == (const pr& x) const {
        return first == x.first && second == x.second;
    }
};

struct hash_pair {
    size_t operator ()(const pr& x) const {
        auto h1 = std :: hash <int>{}(x.first);
        auto h2 = std :: hash <int>{}(x.second);
        return h1 + P * h2;
    }
};

typedef std :: priority_queue <pr, std :: vector <pr>, std :: greater <pr> > PR_Q;
typedef __gnu_pbds :: gp_hash_table <pr, int, hash_pair> HS_T;
typedef std :: vector <pr> GR;

int n, T, t[55], a[105], b[105], dis[MAXN], m1, m2, sumt;

bool vis[MAXN];

HS_T mp;

GR G[MAXN];

PR_Q q;

inline void clr() {
    sumt = 0;
    memset(t, 0, sizeof t);
    memset(vis, 0, sizeof vis);
    memset(dis, INF, sizeof dis);
    HS_T().swap(mp);
    PR_Q().swap(q);
    for(int i = 1; i <= MAXN; i++)
        GR().swap(G[i]);
    dis[1] = 0;
    return ;
}

inline void dijkstra() {
    q.push(pr(1, 0));
    while(!q.empty()) {
        pr rhs = q.top();
        q.pop();
        if(vis[rhs.first])
            continue ;
        vis[rhs.first] = true;
        for(pr v : G[rhs.first]) {
            int to = v.first, wt = v.second;
            if(dis[to] > dis[rhs.first] + wt) {
                dis[to] = dis[rhs.first] + wt;
                q.push(pr(to, dis[to]));
            }
        }
    }
    return ;
}

inline int genGraph() {
    int V = 0;
    pr st = pr(0, 0); mp[st] = ++V;
    int tmpp[105][252];
    memset(tmpp, INF, sizeof tmpp);
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= m1; j++) {
            if(t[i] + a[j] > T)
                continue ;
            pr tmp = pr(i, t[i] + a[j]);
            tmpp[i][j] = t[i] + a[j];
            if(mp[tmp] == 0)
                mp[tmp] = ++V;
        }
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= m2; j++) {
            if(sumt + b[j] > t[i] + T)
                continue ;
            pr tmp = pr(i, sumt - t[i] + b[j]);
            tmpp[i][j + m1] = sumt - t[i] + b[j];
            if(mp[tmp] == 0)
                mp[tmp] = ++V;
        }
    for(int i = 1; i <= n; i++)
        std :: sort(tmpp[i] + 1, tmpp[i] + m1 + m2 + 1);
    pr ed = pr(n + 1, T); mp[ed] = ++V;
    for(int i = 1; i < n; i++)
        for(int j = 1; j <= m1; j++) {
            if(t[i] + a[j] > T || t[i + 1] + a[j] > T)
                continue ;
            pr ux = pr(i, t[i] + a[j]); pr vx = pr(i + 1, t[i + 1] + a[j]);
            G[mp[ux]].push_back(pr(mp[vx], 0));
        }
    for(int i = 2; i <= n; i++)
        for(int j = 1; j <= m2; j++) {
            if(sumt + b[j] > t[i] + T || sumt + b[j] > t[i - 1] + T)
                continue ;
            pr ux = pr(i, sumt - t[i] + b[j]); pr vx = pr(i - 1, sumt - t[i - 1] + b[j]);
            G[mp[ux]].push_back(pr(mp[vx], 0));
        }
    for(int i = 1; i <= n; i++)
        for(int j = 1; j < m1 + m2; j++) {
            if(tmpp[i][j] > T || tmpp[i][j + 1] > T)
                continue ;
            pr ux = pr(i, tmpp[i][j]); pr vx = pr(i, tmpp[i][j + 1]);
            G[mp[ux]].push_back(pr(mp[vx], tmpp[i][j + 1] - tmpp[i][j]));
        }
    for(int i = 1; i <= m1 + m2; i++) {
        pr ux = pr(n, tmpp[n][i]); pr vx = pr(1, tmpp[1][i]);
        if(tmpp[1][i] <= T)
            G[1].push_back(pr(mp[vx], tmpp[1][i]));
        if(T >= tmpp[n][i])
            G[mp[ux]].push_back(pr(V, T - tmpp[n][i]));
    }
    return V;
}

int main() {
    int pcnt = 0;
    scanf("%d", &n);
    do {
        ++pcnt;
        clr();
        scanf("%d", &T);
        int dt = 0;
        for(int i = 2; i <= n; i++) {
            scanf("%d", &dt);
            t[i] = dt + t[i - 1];
            sumt += dt;
        }
        scanf("%d", &m1);
        for(int i = 1; i <= m1; i++)
            scanf("%d", a + i);
        scanf("%d", &m2);
        for(int i = 1; i <= m2; i++)
            scanf("%d", b + i);
        int edx = genGraph();
        dijkstra();
        if(dis[edx] == INF)
            printf("Case Number %d: impossible\n", pcnt);
        else
            printf("Case Number %d: %d\n", pcnt, dis[edx]);
        scanf("%d", &n);
    }while(n != 0);
    return 0;
}