Codeforces 677D - Vanya and Treasure

#include <bits/stdc++.h>
using namespace std;
#define INF 0x7f7f7f7f
const int maxn = 300+10;
int dp[maxn][maxn], vis[maxn][maxn], cnt[maxn*maxn], cn[maxn*maxn];
struct Poi
{
    int x, y, p;
    Poi(){}
    Poi(int x, int y, int p):x(x), y(y), p(p){}
    bool operator<(const Poi &a)const
    {
        return p>a.p;
    }
}poi[maxn*maxn];
int dx[]={0,1,0,-1};
int dy[]={1,0,-1,0};

int n, m, p, l;
int cmp(const Poi &a, const Poi &b)
{
    return a.p < b.p;
}
int dis(int a, int b)
{
    return abs(poi[a].x-poi[b].x) + abs(poi[a].y-poi[b].y);
}

void bfs(int ti)
{
    int x, y;

    memset(vis, INF, sizeof(vis));
    int tcnt=0, len = n*m;
    queue<Poi> pq;
    for(int i=cn[ti-1]-cnt[ti-1];i<cn[ti-1];++i)
    {
        x=poi[i].x; y=poi[i].y;
        pq.push(Poi(x, y, dp[y][x]));
    }
    while(!pq.empty())
    {
        Poi tp = pq.front(); pq.pop();
        for(int i=0;i<4;++i)
        {
            int tx=tp.x+dx[i], ty=tp.y+dy[i];
            if(ty>=1&&tx>=1&&ty<=n&&tx<=m&&vis[ty][tx]>tp.p+1)
            {
                vis[ty][tx]=tp.p+1;
                tcnt++;
                pq.push(Poi(tx, ty, tp.p+1));
            }
        }
    }
    for(int j=cn[ti-1];j<cn[ti];++j)
    {
        x=poi[j].x; y=poi[j].y;
        dp[y][x] = vis[y][x];
    }
}
int main()
{
    l=0;
    poi[l++]=Poi(1,1,0);
    cnt[0]=1;
    memset(dp, INF, sizeof(dp));
    int x, y, tx, ty, i, j, z, t;

    scanf("%d%d%d", &n, &m, &p);
    for(i=1;i<=n;++i)
        for(j=1;j<=m;++j)
        {
            scanf("%d", &t);
            cnt[t]++;
            poi[l++]=Poi(j, i, t);
        }
    sort(poi, poi+l, cmp);
    cn[0]=1; for(i=1;i<=p;++i) cn[i]=cn[i-1]+cnt[i];
    for(i=cn[0];i<cn[1];++i) dp[poi[i].y][poi[i].x]=dis(0,i);
    for(i=2;i<=p;++i)
    {
        if(cnt[i]*cnt[i-1]>=n*m) bfs(i);
        else 
        {
            for(j=cn[i-1];j<cn[i];++j)
            {
                y=poi[j].y; x=poi[j].x;
                for(z=cn[i-1]-cnt[i-1];z<cn[i-1];++z)
                {
                    ty=poi[z].y; tx=poi[z].x;
                    dp[y][x]=min(dp[y][x], dp[ty][tx] + dis(j, z));
                }
            }
        }
    }
//    cout<<"---"<<endl; for(int i=1;i<=n;++i) for(int j=1;j<=m;++j) printf("%d%c", dp[i][j], j==m ? ‘\n‘ : ‘ ‘);
    printf("%d\n", dp[poi[l-1].y][poi[l-1].x]);
    

    return 0;
}