Submission #917948

#	Time	Username	Problem	Language	Result	Execution time	Memory
917948		nightfal	Ancient Books (IOI17_books)	C++14	100 / 100	103 ms	20052 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);
}

pair<int,int> extend(int l, int r, vector<int>& lmost, vector<int>& rmost) {
    while(l > min(lmost[l],lmost[r]) || r < max(rmost[l],rmost[r])) {
        l=min(l,min(lmost[l],lmost[r])); 
        r=max(r,max(rmost[r],rmost[l]));
    }
    return make_pair(l,r);
} 

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

    int n = p.size();

    // curtail ignorable head and tail.
    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;

    long long totalJumps=0;
    for(int i=start; i<=end; i++) totalJumps += abs(p[i]-i);

    int l = min(s,p[s]), r=max(s,p[s]); 
    vector<int> lmost(n), rmost(n); lmost[s] = min(s,p[s]); rmost[s] = max(s,p[s]);
    for(int i=s-1; i>=start; i--) {lmost[i] = min(lmost[i+1],p[i]); rmost[i] = max(rmost[i+1],p[i]);}
    for(int i=s+1; i<=end ; i++) {lmost[i] = min(lmost[i-1],p[i]); rmost[i] = max(rmost[i-1],p[i]);}
    tie(l,r) = extend(l,r,lmost,rmost);

    long long totalMoves=0, rMoves=0, lMoves=0;

    while(start<l || r<end) {
        int l2, r2;
        if(r<end && (l<=start || rMoves < lMoves)) {
            r++; rMoves++;
            tie(l2,r2) = extend(l,r,lmost,rmost);
            if (l2<l) {totalMoves += rMoves; rMoves = lMoves = 0;}
        }
        else {
            l--; lMoves++;
            tie(l2,r2) = extend(l,r,lmost,rmost);
            if (r<r2) {totalMoves += lMoves; rMoves = lMoves = 0;}
        }
        l = l2; r = r2;
    }
    totalMoves += rMoves + lMoves;
    // printf("totalMoves=%d, jumps=%d\n",totalMoves,jumps);
    return totalMoves*2+totalJumps;
}

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) {
      |                  ~~~~~~~^~~~~~~

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