UVa/11663 - GrayInc/11663.2.cpp

   1 using namespace std;
   2 #include <algorithm>
   3 #include <iostream>
   4 #include <iterator>
   5 #include <sstream>
   6 #include <fstream>
   7 #include <cassert>
   8 #include <climits>
   9 #include <cstdlib>
  10 #include <cstring>
  11 #include <string>
  12 #include <cstdio>
  13 #include <vector>
  14 #include <cmath>
  15 #include <queue>
  16 #include <deque>
  17 #include <stack>
  18 #include <list>
  19 #include <map>
  20 #include <set>
  21
  22 template <class T> string toStr(const T &x){ stringstream s; s << x; return s.str(); }
  23 template <class T> int toInt(const T &x){ stringstream s; s << x; int r; s >> r; return r; }
  24
  25 #define For(i, a, b) for (int i=(a); i<(b); ++i)
  26 #define foreach(x, v) for (typeof (v).begin() x = (v).begin(); x != (v).end(); ++x)
  27 #define D(x) cout << #x " = " << (x) << endl
  28
  29 int next(const string &s, int i);
  30 int prev(const string &s, int i);
  31
  32 bool looksLike0000(const string &s, int i){
  33   for (; i<s.size(); ++i) if (s[i] != '0') return false;
  34   return true;
  35 }
  36
  37 bool looksLike1000(const string &s, int i){
  38   if (s[i] != '1') return false;
  39   for (++i; i<s.size(); ++i) if (s[i] != '0') return false;
  40   return true;
  41 }
  42
  43 int next(const string &s, int i){
  44   if (i == s.size() - 1) return i;
  45   if (s[i] == '0'){
  46     if (looksLike1000(s, i+1)){
  47       return i;
  48     }else{
  49       return next(s, i+1);
  50     }
  51   }else{
  52     if (looksLike0000(s, i+1)){
  53       return i;
  54     }else{
  55       return prev(s, i+1);
  56     }
  57   }
  58 }
  59
  60 int prev(const string &s, int i){
  61   if (i == s.size() - 1) return i;
  62   if (s[i] == '0'){
  63     if (looksLike0000(s, i+1)){
  64       return i;
  65     }else{
  66       return prev(s, i+1);
  67     }
  68   }else{
  69     if (looksLike1000(s, i+1)){
  70       return i;
  71     }else{
  72       return next(s, i+1);
  73     }
  74   }
  75 }
  76
  77 int main(){
  78   int m;
  79   string s;
  80   while (cin >> m >> s && m){
  81     while (m--){
  82       int where = next(s, 0);
  83       s[where] = s[where] == '0' ? '1' : '0';
  84     }
  85     cout << s << endl;
  86   }
  87   return 0;
  88 }