Submission #916000

#	Time	Username	Problem	Language	Result	Execution time	Memory
916000		nightfal	Ancient Books (IOI17_books)	C++14	50 / 100	82 ms	12120 KiB

books

#include <cstdio>
#include <vector>
#include <cassert>
#include <cstdlib>
#include <tuple>
#include <climits>

using namespace std;

bool isSubtask3(int s) {return s==0;}
bool isSubtask4(int n) {return n<=1000;}

long long subtask3(vector<int> p, int s = 0, int e = -1 , int dir = 1) {
    int n = p.size(), last = s;
    if (e==-1) e = n-1;
    long long total = 0;

    for(int i=s; dir==1 && i<=e || dir==-1 && i>=e; i += dir) {
        if (i==p[i]) continue;
        if (dir*(i-last) > 0) total += abs(i-last)*2;
        total += abs(p[i]-i);
        last = dir==1? max(last,p[i]):min(last,p[i]);
    }
	return total;
}

long long cal(vector<int> p, int l, int r, int lmost, int rmost, vector<vector<long long>>& dp) {
    if (dp[l][r]!=LLONG_MAX) return dp[l][r];
    int n = p.size(); 
    long long temp1=LLONG_MAX, temp2=LLONG_MAX;
    if (l>0) {
        temp1 = abs(p[l-1]-(l-1)); if(l-1 < lmost) temp1 += 2;
        int lmostN = min(lmost,min(l-1,p[l-1])), rmostN = max(rmost,p[l-1]);
        temp1 += cal(p,l-1,r,lmostN,rmostN,dp); 
    }
    if (r<n-1) {
        temp2 = abs(p[r+1]-(r+1)); if(r+1 > rmost) temp2 += 2;
        int lmostN = min(lmost,p[r+1]), rmostN = max(rmost,max(r+1,p[r+1]));
        temp2 += cal(p,l,r+1,lmostN,rmostN,dp); 
    }
    dp[l][r] = min(temp1,temp2);
    return dp[l][r];
}

long long subtask4(vector<int> p, int s) {
    int n = p.size();
    // long long move = 0;
    
    int start; for(start = 0; start < s; start++) if(start!=p[start]) break;
    int end; for(end = n-1; end > s; end--) if(end!=p[end]) break;
    for(int i = 0; i <= end-start; i++) p[i] = p[i+start]-start;
    s -= start; n = end-start+1; p.resize(n); 
    vector<vector<long long>> dp(n,vector<long long>(n,LLONG_MAX));
    dp[0][n-1]=0;

    int l=s, r=s, lmost = min(s,p[s]), rmost = max(s,p[s]);
    return cal(p,l,r,lmost,rmost,dp)+abs(p[s]-s);
}

tuple<int,int,long long> extend(vector<int> p, int l, int r, int lmost, int rmost, int move) {
    int n = p.size();
    while(l> lmost || r < rmost) {
        int idx;
        if (l > max(lmost,0)) idx == --l;
        else if (r < min(rmost,n-1)) idx == ++r;
        move += abs(p[idx]-idx);
        lmost = min(lmost,p[idx]); 
        rmost = max(rmost,p[idx]);
    }
    return make_tuple(l,r,move);
} 

long long fulltask(vector<int> p, int s) {

    int n = p.size();

    int start; for(start = 0; start < s; start++) if(start!=p[start]) break;
    int end; for(end = n-1; end > s; end--) if(end!=p[end]) break;
    for(int i = 0; i <= end-start; i++) p[i] = p[i+start]-start;
    s -= start; n = end-start+1; p.resize(n); 

    int l=s, r=s, lmost = min(s,p[s]), rmost = max(s,p[s]);
    long long total=abs(p[s]-s), sumL=0, sumR=0, moveL=0, moveR=0;
    

    while(0<l || r<n-1) {
        // printf("total=%d, sumL=%d, sumR=%d, moveL=%d, moveR=%d\n",total,sumL,sumR,moveL,moveR);
        // printf("l=%d, r=%d, lmost=%d, rmost=%d\n\n",l,r,lmost,rmost);

        if(r < n-1 && (l <= 0 || moveR < moveL || moveR == moveL && r < rmost)) {
            if(rmost <= r) moveR++;
            r++;
            sumR += abs(p[r]-r);
            rmost = max(rmost,max(r,p[r]));
            lmost  = min(lmost,p[r]);
            if (lmost <= l) {moveL = 0; total+=sumR+moveR*2; moveR=0; sumR=0;}
        } 
        else if(0 < l && (r >= n-1 || moveR > moveL || moveR == moveL && r >= rmost)) {
            if (l <= lmost) moveL++;
            l--;
            sumL += abs(p[l]-l); 
            lmost  = min(lmost,min(l,p[l]));
            rmost = max(rmost,p[l]);
            if (r <= rmost) {moveR = 0; total+=sumL+moveL*2; moveL=0; sumL=0;}            
            l--;
        }
    }
    // printf("total=%d, sumL=%d, sumR=%d, moveL=%d, moveR=%d\n",total,sumL,sumR,moveL,moveR);
    // printf("l=%d, r=%d, lmost=%d, rmost=%d\n",l,r,lmost,rmost);
 
    if(sumL) total += sumL + moveL*2; // ??
    if(sumR) total += sumR + moveR*2; // ??
    return total;
}

long long minimum_walk(std::vector<int> p, int s) {
    // if (isSubtask3(s)) return subtask3(p);
    // if (isSubtask4(s)) return subtask4(p,s);
    return fulltask(p,s);
}

Compilation message (stderr)

books.cpp: In function 'long long int subtask3(std::vector<int>, int, int, int)':
books.cpp:18:25: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   18 |     for(int i=s; dir==1 && i<=e || dir==-1 && i>=e; i += dir) {
      |                  ~~~~~~~^~~~~~~
books.cpp: In function 'std::tuple<int, int, long long int> extend(std::vector<int>, int, int, int, int, int)':
books.cpp:64:35: warning: value computed is not used [-Wunused-value]
   64 |         if (l > max(lmost,0)) idx == --l;
      |                               ~~~~^~~~~~
books.cpp:65:42: warning: value computed is not used [-Wunused-value]
   65 |         else if (r < min(rmost,n-1)) idx == ++r;
      |                                      ~~~~^~~~~~
books.cpp: In function 'long long int fulltask(std::vector<int>, int)':
books.cpp:90:66: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   90 |         if(r < n-1 && (l <= 0 || moveR < moveL || moveR == moveL && r < rmost)) {
      |                                                   ~~~~~~~~~~~~~~~^~~~~~~~~~~~
books.cpp:98:71: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   98 |         else if(0 < l && (r >= n-1 || moveR > moveL || moveR == moveL && r >= rmost)) {
      |                                                        ~~~~~~~~~~~~~~~^~~~~~~~~~~~~
books.cpp: In function 'std::tuple<int, int, long long int> extend(std::vector<int>, int, int, int, int, int)':
books.cpp:66:26: warning: 'idx' is used uninitialized in this function [-Wuninitialized]
   66 |         move += abs(p[idx]-idx);
      |                          ^

• Subtask 1: 12 / 12
• Subtask 2: 10 / 10
• Subtask 3: 28 / 28
• Subtask 4: 0 / 20
• Subtask 5: 0 / 30