Submission #1226986

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Source Code Expand

#include <queue>
#include <map>
#include <cstdio>
#include <cstring>
#include <cassert>
#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

#define TRACE(x) cerr << #x << " = " << x << endl
#define REP(i, n) for (int i=0; i<n; i++)
#define FOR(i, a, b) for (int i=(a); i<(b); i++)
#define _ << " " <<

typedef long long ll;
typedef pair<int, int> P;
#define X first
#define Y second

const int MAX = 1<<20, ALFA = 26;

char poc[MAX], kraj[MAX];
int pozl[MAX][ALFA];
int pref[MAX];
int n;

map <string, int> M;
queue <string> Q;

void rek(const string &pat, string s, int poz, int val) {
  if (poz == n) {
    if (M.find(s) == M.end()) {
      M[s] = val;
      Q.push(s);      
    }    
    return;
  }

  s[poz] = pat[poz];
  rek(pat, s, poz+1, val);

  if (poz) {
    s[poz] = s[poz-1];
    rek(pat, s, poz+1, val);
  }
}

int brute() {
  M.clear();
  for (; !Q.empty(); Q.pop());

  string pc = poc, kr = kraj;
  M[pc] = 0;

  TRACE(pc _ kr);

  Q.push(pc);

  for (; !Q.empty(); ) {
    string tmp = Q.front(); Q.pop();
    if (tmp == kr) return M[tmp];
    rek(tmp, tmp, 0, M[tmp]+1);
  }
  return -1;
}

void gen() {
  n = rand() % 6 + 1;
  REP(i, n) poc[i] = (char) (rand() % 2 + 'a');
  REP(i, n) kraj[i] = (char) (rand() % 2 + 'a');
  poc[n] = kraj[n] = 0;

  // n = 4;
  // poc[0] = 'a'; poc[1] = 'b'; poc[2] = 'a'; poc[3] = 'a'; poc[4] = 0;
  // kraj[0] = 'a'; kraj[1] = 'a'; kraj[2] = 'b'; kraj[3] = 'b'; kraj[4] = 0;
}

const int TOUR = 1<<20;
int t[2*TOUR];

void stavi(int pos, int val) {
  pos += TOUR;
  for (; pos; pos /= 2)
    t[pos] = max(t[pos], val);
}

int vrati(int pos, int lo, int hi, int begin, int end) {
  if (lo >= end || hi <= begin) return 0;
  if (lo >= begin && hi <= end) return t[pos];
  return max(vrati(2*pos+0, lo, (lo+hi)/2, begin, end),
	     vrati(2*pos+1, (lo+hi)/2, hi, begin, end));
}

int solve() {
  memset(t, 0, sizeof t);
  memset(pozl, -1, sizeof pozl);

  REP(i, n) {
    if (i)
      memcpy(pozl[i], pozl[i-1], sizeof pozl[i]);
    pozl[i][poc[i]-'a'] = i;
  }
  
  int poz = n-1, rje = 0;
  for (int i=n-1; i>=0; i--) {
    poz = min(poz, i);

    int tmp = pozl[poz][kraj[i]-'a'];
    if (tmp == -1) return -1;
  
    int val = vrati(1, 0, TOUR, tmp+1, i+1) + (tmp != i);
    rje = max(rje, val);
    stavi(tmp, val);
    rje = max(rje, val);

    poz = tmp;
  }  

  return rje;
}

int main()
{
  scanf("%d %s %s", &n, poc, kraj);
  printf("%d\n", solve());
  //   TRACE(solve() _ brute());
  return 0;
  
  for (;;) {
    gen();
    TRACE(n _ poc _ kraj);
    int sl = solve(), br = brute();
    TRACE(sl _ br);
    assert(sl == br);
  }

  return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:126:35: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %s %s", &n, poc, kraj);
                                   ^

Judge Result