UVA 1596 Bug Hunt

Posted 2022-02-05 zaq19970105

题目链接：https://vjudge.net/problem/UVA-1596

题目翻译摘自《算法禁赛入门经典》

题目大意

　　输入并模拟执行一段程序，输出第一个bug所在的行。每行程序有两种可能：

1. 数组定义，格式为 arr[size]。例如 a[10] 或者 b[5]，可用下标分别是 0～9 和 0～4。定义之后所有元素均为未初始化状态。
2. 赋值语句，格式为 arr[index]=value。例如 a[0]=3 或者 a[a[0]]=a[1]。

　　赋值语句可能会出现两种bug：

1. 下标 index 越界；
2. 使用未初始化的变量（index 和 value 都可能出现这种情况）。

　　程序不超过1000行，每行不超过80个字符且所有常数均为小于 2³¹ 的非负整数。

分析

　　总体来说没什么难度，只要耐心就能做对。

代码如下

  1 #include <bits/stdc++.h>
  2 using namespace std;
  3  
  4 #define INIT() ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
  5 #define Rep(i,n) for (int i = 0; i < (n); ++i)
  6 #define For(i,s,t) for (int i = (s); i <= (t); ++i)
  7 #define rFor(i,t,s) for (int i = (t); i >= (s); --i)
  8 #define ForLL(i, s, t) for (LL i = LL(s); i <= LL(t); ++i)
  9 #define rForLL(i, t, s) for (LL i = LL(t); i >= LL(s); --i)
 10 #define foreach(i,c) for (__typeof(c.begin()) i = c.begin(); i != c.end(); ++i)
 11 #define rforeach(i,c) for (__typeof(c.rbegin()) i = c.rbegin(); i != c.rend(); ++i)
 12  
 13 #define pr(x) cout << #x << " = " << x << "  "
 14 #define prln(x) cout << #x << " = " << x << endl
 15  
 16 #define LOWBIT(x) ((x)&(-x))
 17  
 18 #define ALL(x) x.begin(),x.end()
 19 #define INS(x) inserter(x,x.begin())
 20 #define UNIQUE(x) x.erase(unique(x.begin(), x.end()), x.end())
 21  
 22 #define ms0(a) memset(a,0,sizeof(a))
 23 #define msI(a) memset(a,inf,sizeof(a))
 24 #define msM(a) memset(a,-1,sizeof(a))
 25 
 26 #define MP make_pair
 27 #define PB push_back
 28 #define ft first
 29 #define sd second
 30  
 31 template<typename T1, typename T2>
 32 istream &operator>>(istream &in, pair<T1, T2> &p) 
 33     in >> p.first >> p.second;
 34     return in;
 35 
 36  
 37 template<typename T>
 38 istream &operator>>(istream &in, vector<T> &v) 
 39     for (auto &x: v)
 40         in >> x;
 41     return in;
 42 
 43  
 44 template<typename T1, typename T2>
 45 ostream &operator<<(ostream &out, const std::pair<T1, T2> &p) 
 46     out << "[" << p.first << ", " << p.second << "]" << "\n";
 47     return out;
 48 
 49 
 50 inline int gc()
 51     static const int BUF = 1e7;
 52     static char buf[BUF], *bg = buf + BUF, *ed = bg;
 53     
 54     if(bg == ed) fread(bg = buf, 1, BUF, stdin);
 55     return *bg++;
 56  
 57 
 58 inline int ri()
 59     int x = 0, f = 1, c = gc();
 60     for(; c<48||c>57; f = c==‘-‘?-1:f, c=gc());
 61     for(; c>47&&c<58; x = x*10 + c - 48, c=gc());
 62     return x*f;
 63 
 64 
 65 template<class T>
 66 inline string toString(T x) 
 67     ostringstream sout;
 68     sout << x;
 69     return sout.str();
 70 
 71 
 72 inline int toInt(string s) 
 73     int v;
 74     istringstream sin(s);
 75     sin >> v;
 76     return v;
 77 
 78 
 79 //min <= aim <= max
 80 template<typename T>
 81 inline bool BETWEEN(const T aim, const T min, const T max) 
 82     return min <= aim && aim <= max;
 83 
 84  
 85 typedef long long LL;
 86 typedef unsigned long long uLL;
 87 typedef pair< double, double > PDD;
 88 typedef pair< int, int > PII;
 89 typedef pair< int, PII > PIPII;
 90 typedef pair< string, int > PSI;
 91 typedef pair< int, PSI > PIPSI;
 92 typedef set< int > SI;
 93 typedef set< PII > SPII;
 94 typedef vector< int > VI;
 95 typedef vector< double > VD;
 96 typedef vector< VI > VVI;
 97 typedef vector< SI > VSI;
 98 typedef vector< PII > VPII;
 99 typedef map< int, int > MII;
100 typedef map< int, string > MIS;
101 typedef map< int, PII > MIPII;
102 typedef map< PII, int > MPIII;
103 typedef map< string, int > MSI;
104 typedef map< string, string > MSS;
105 typedef map< PII, string > MPIIS;
106 typedef map< PII, PII > MPIIPII;
107 typedef multimap< int, int > MMII;
108 typedef multimap< string, int > MMSI;
109 //typedef unordered_map< int, int > uMII;
110 typedef pair< LL, LL > PLL;
111 typedef vector< LL > VL;
112 typedef vector< VL > VVL;
113 typedef priority_queue< int > PQIMax;
114 typedef priority_queue< int, VI, greater< int > > PQIMin;
115 const double EPS = 1e-8;
116 const LL inf = 0x7fffffff;
117 const LL infLL = 0x7fffffffffffffffLL;
118 const LL mod = 1e9 + 7;
119 const int maxN = 1e4 + 7;
120 const LL ONE = 1;
121 const LL evenBits = 0xaaaaaaaaaaaaaaaa;
122 const LL oddBits = 0x5555555555555555;
123 
124 struct Var
125     string name;
126     int bios;
127     
128     bool operator< (const Var &x) const 
129         return name < x.name || name == x.name && bios < x.bios;
130     
131 ;
132 
133 string tmp; 
134 MSI arr_len; // 记录数组名和对应长度
135 map< Var, int > vars; // 记录初始化的变量和对应值 
136 int ans;
137 
138 bool isOut(Var x) 
139     return x.bios >= arr_len[x.name];
140 
141 
142 bool isAssign(Var x) 
143     return vars.find(x) != vars.end();
144 
145 
146 // 解析成功返回true，如果有嵌套，那么可能解析失败，此时返回false 
147 bool analysis(string s, Var &x) 
148     x.name = s.substr(0, s.find("["));
149     s = s.substr(s.find("[") + 1);
150     s.pop_back();
151     
152     if(s.back() == ‘]‘) 
153         Var y;
154         if(analysis(s, y) && !isOut(y), isAssign(y)) x.bios = vars[y];
155         else return false;
156     
157     else x.bios = toInt(s);
158     return true;
159 
160 
161 int main()
162     //freopen("MyOutput.txt","w",stdout);
163     //freopen("input.txt","r",stdin);
164     //INIT();
165     while(getline(cin, tmp)) 
166         if(tmp == ".") break; 
167         arr_len.clear();
168         vars.clear();
169         ans = 0; 
170         
171         do 
172             if(tmp == ".") break;
173             ++ans;
174             Var x, y;
175             
176             if(tmp.find("=") == string::npos)  // 数组声明 
177                 if(analysis(tmp, x)) arr_len[x.name] = x.bios;
178                 else break;
179             
180             else  // 赋值 
181                 string X = tmp.substr(0, tmp.find("="));
182                 string Y = tmp.substr(tmp.find("=") + 1);
183                 
184                 if(analysis(X, x) && !isOut(x)) 
185                     if(isdigit(Y[0])) vars[x] = toInt(Y);
186                     else 
187                         if(!analysis(Y, y) || isOut(y) || !isAssign(y)) break;
188                         vars[x] = vars[y];
189                     
190                 
191                 else break;
192             
193         while(getline(cin, tmp));
194         
195         if(tmp == ".") ans = 0;
196         
197         do  if(tmp == ".") break; while(getline(cin, tmp)); // 处理多余的输入 
198         
199         cout << ans << endl;
200     
201     return 0;
202 

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