UVA 1596 Bug Hunt

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

#include <bits/stdc++.h>
using namespace std;
 
#define INIT() ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define Rep(i,n) for (int i = 0; i < (n); ++i)
#define For(i,s,t) for (int i = (s); i <= (t); ++i)
#define rFor(i,t,s) for (int i = (t); i >= (s); --i)
#define ForLL(i, s, t) for (LL i = LL(s); i <= LL(t); ++i)
#define rForLL(i, t, s) for (LL i = LL(t); i >= LL(s); --i)
#define foreach(i,c) for (__typeof(c.begin()) i = c.begin(); i != c.end(); ++i)
#define rforeach(i,c) for (__typeof(c.rbegin()) i = c.rbegin(); i != c.rend(); ++i)
 
#define pr(x) cout << #x << " = " << x << "  "
#define prln(x) cout << #x << " = " << x << endl
 
#define LOWBIT(x) ((x)&(-x))
 
#define ALL(x) x.begin(),x.end()
#define INS(x) inserter(x,x.begin())
#define UNIQUE(x) x.erase(unique(x.begin(), x.end()), x.end())
 
#define ms0(a) memset(a,0,sizeof(a))
#define msI(a) memset(a,inf,sizeof(a))
#define msM(a) memset(a,-1,sizeof(a))

#define MP make_pair
#define PB push_back
#define ft first
#define sd second
 
template<typename T1, typename T2>
istream &operator>>(istream &in, pair<T1, T2> &p) {
    in >> p.first >> p.second;
    return in;
}
 
template<typename T>
istream &operator>>(istream &in, vector<T> &v) {
    for (auto &x: v)
        in >> x;
    return in;
}
 
template<typename T1, typename T2>
ostream &operator<<(ostream &out, const std::pair<T1, T2> &p) {
    out << "[" << p.first << ", " << p.second << "]" << "
";
    return out;
}

inline int gc(){
    static const int BUF = 1e7;
    static char buf[BUF], *bg = buf + BUF, *ed = bg;
    
    if(bg == ed) fread(bg = buf, 1, BUF, stdin);
    return *bg++;
} 

inline int ri(){
    int x = 0, f = 1, c = gc();
    for(; c<48||c>57; f = c=='-'?-1:f, c=gc());
    for(; c>47&&c<58; x = x*10 + c - 48, c=gc());
    return x*f;
}

template<class T>
inline string toString(T x) {
    ostringstream sout;
    sout << x;
    return sout.str();
}

inline int toInt(string s) {
    int v;
    istringstream sin(s);
    sin >> v;
    return v;
}

//min <= aim <= max
template<typename T>
inline bool BETWEEN(const T aim, const T min, const T max) {
    return min <= aim && aim <= max;
}
 
typedef long long LL;
typedef unsigned long long uLL;
typedef pair< double, double > PDD;
typedef pair< int, int > PII;
typedef pair< int, PII > PIPII;
typedef pair< string, int > PSI;
typedef pair< int, PSI > PIPSI;
typedef set< int > SI;
typedef set< PII > SPII;
typedef vector< int > VI;
typedef vector< double > VD;
typedef vector< VI > VVI;
typedef vector< SI > VSI;
typedef vector< PII > VPII;
typedef map< int, int > MII;
typedef map< int, string > MIS;
typedef map< int, PII > MIPII;
typedef map< PII, int > MPIII;
typedef map< string, int > MSI;
typedef map< string, string > MSS;
typedef map< PII, string > MPIIS;
typedef map< PII, PII > MPIIPII;
typedef multimap< int, int > MMII;
typedef multimap< string, int > MMSI;
//typedef unordered_map< int, int > uMII;
typedef pair< LL, LL > PLL;
typedef vector< LL > VL;
typedef vector< VL > VVL;
typedef priority_queue< int > PQIMax;
typedef priority_queue< int, VI, greater< int > > PQIMin;
const double EPS = 1e-8;
const LL inf = 0x7fffffff;
const LL infLL = 0x7fffffffffffffffLL;
const LL mod = 1e9 + 7;
const int maxN = 1e4 + 7;
const LL ONE = 1;
const LL evenBits = 0xaaaaaaaaaaaaaaaa;
const LL oddBits = 0x5555555555555555;

struct Var{
    string name;
    int bios;
    
    bool operator< (const Var &x) const {
        return name < x.name || name == x.name && bios < x.bios;
    }
};

string tmp; 
MSI arr_len; // 记录数组名和对应长度
map< Var, int > vars; // 记录初始化的变量和对应值 
int ans;

bool isOut(Var x) {
    return x.bios >= arr_len[x.name];
}

bool isAssign(Var x) {
    return vars.find(x) != vars.end();
}

// 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 
bool analysis(string s, Var &x) {
    x.name = s.substr(0, s.find("["));
    s = s.substr(s.find("[") + 1);
    s.pop_back();
    
    if(s.back() == ']') {
        Var y;
        if(analysis(s, y) && !isOut(y), isAssign(y)) x.bios = vars[y];
        else return false;
    }
    else x.bios = toInt(s);
    return true;
}

int main(){
    //freopen("MyOutput.txt","w",stdout);
    //freopen("input.txt","r",stdin);
    //INIT();
    while(getline(cin, tmp)) {
        if(tmp == ".") break; 
        arr_len.clear();
        vars.clear();
        ans = 0; 
        
        do {
            if(tmp == ".") break;
            ++ans;
            Var x, y;
            
            if(tmp.find("=") == string::npos) { // 数组声明 
                if(analysis(tmp, x)) arr_len[x.name] = x.bios;
                else break;
            }
            else { // 赋值 
                string X = tmp.substr(0, tmp.find("="));
                string Y = tmp.substr(tmp.find("=") + 1);
                
                if(analysis(X, x) && !isOut(x)) {
                    if(isdigit(Y[0])) vars[x] = toInt(Y);
                    else {
                        if(!analysis(Y, y) || isOut(y) || !isAssign(y)) break;
                        vars[x] = vars[y];
                    }
                }
                else break;
            }
        }while(getline(cin, tmp));
        
        if(tmp == ".") ans = 0;
        
        do { if(tmp == ".") break; }while(getline(cin, tmp)); // 处理多余的输入 
        
        cout << ans << endl;
    }
    return 0;
}