牛客 公式字符串求值

题目链接:https://www.nowcoder.com/practice/c590e97ee1f6462d871430feee055d25?tpId=101&tqId=33196&tPage=1&rp=1&ru=/ta/programmer-code-interview-guide&qru=/ta/programmer-code-interview-guide/question-ranking

题目大意:

  略。

分析:

  递归基本题。

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 < (int)(n); ++i)
  6 #define For(i,s,t) for (int i = (int)(s); i <= (int)(t); ++i)
  7 #define rFor(i,t,s) for (int i = (int)(t); i >= (int)(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 #define REMOVE(x, c) x.erase(remove(x.begin(), x.end(), c), x.end()); // 删去 x 中所有 c 
 22 #define TOLOWER(x) transform(x.begin(), x.end(), x.begin(),::tolower);
 23 #define TOUPPER(x) transform(x.begin(), x.end(), x.begin(),::toupper);
 24  
 25 #define ms0(a) memset(a,0,sizeof(a))
 26 #define msI(a) memset(a,0x3f,sizeof(a))
 27 #define msM(a) memset(a,-1,sizeof(a))
 28 
 29 #define MP make_pair
 30 #define PB push_back
 31 #define ft first
 32 #define sd second
 33  
 34 template<typename T1, typename T2>
 35 istream &operator>>(istream &in, pair<T1, T2> &p) {
 36     in >> p.first >> p.second;
 37     return in;
 38 }
 39  
 40 template<typename T>
 41 istream &operator>>(istream &in, vector<T> &v) {
 42     for (auto &x: v)
 43         in >> x;
 44     return in;
 45 }
 46 
 47 template<typename T>
 48 ostream &operator<<(ostream &out, vector<T> &v) {
 49     Rep(i, v.size()) out << v[i] << " \n"[i == v.size() - 1];
 50     return out;
 51 }
 52  
 53 template<typename T1, typename T2>
 54 ostream &operator<<(ostream &out, const std::pair<T1, T2> &p) {
 55     out << "[" << p.first << ", " << p.second << "]" << "\n";
 56     return out;
 57 }
 58 
 59 inline int gc(){
 60     static const int BUF = 1e7;
 61     static char buf[BUF], *bg = buf + BUF, *ed = bg;
 62     
 63     if(bg == ed) fread(bg = buf, 1, BUF, stdin);
 64     return *bg++;
 65 } 
 66 
 67 inline int ri(){
 68     int x = 0, f = 1, c = gc();
 69     for(; c<48||c>57; f = c=='-'?-1:f, c=gc());
 70     for(; c>47&&c<58; x = x*10 + c - 48, c=gc());
 71     return x*f;
 72 }
 73 
 74 template<class T>
 75 inline string toString(T x) {
 76     ostringstream sout;
 77     sout << x;
 78     return sout.str();
 79 }
 80 
 81 inline int toInt(string s) {
 82     int v;
 83     istringstream sin(s);
 84     sin >> v;
 85     return v;
 86 }
 87 
 88 //min <= aim <= max
 89 template<typename T>
 90 inline bool BETWEEN(const T aim, const T min, const T max) {
 91     return min <= aim && aim <= max;
 92 }
 93 
 94 typedef unsigned int uI;
 95 typedef long long LL;
 96 typedef unsigned long long uLL;
 97 typedef vector< int > VI;
 98 typedef vector< bool > VB;
 99 typedef vector< char > VC;
100 typedef vector< double > VD;
101 typedef vector< string > VS;
102 typedef vector< LL > VL;
103 typedef vector< VI > VVI;
104 typedef vector< VB > VVB;
105 typedef vector< VS > VVS;
106 typedef vector< VL > VVL;
107 typedef vector< VVI > VVVI;
108 typedef vector< VVL > VVVL;
109 typedef pair< int, int > PII;
110 typedef pair< LL, LL > PLL;
111 typedef pair< int, string > PIS;
112 typedef pair< string, int > PSI;
113 typedef pair< string, string > PSS;
114 typedef pair< double, double > PDD;
115 typedef vector< PII > VPII;
116 typedef vector< PLL > VPLL;
117 typedef vector< VPII > VVPII;
118 typedef vector< VPLL > VVPLL;
119 typedef vector< VS > VVS;
120 typedef map< int, int > MII;
121 typedef unordered_map< int, int > uMII;
122 typedef map< LL, LL > MLL;
123 typedef map< string, int > MSI;
124 typedef map< int, string > MIS;
125 typedef multiset< int > mSI;
126 typedef multiset< char > mSC;
127 typedef set< int > SI;
128 typedef stack< int > SKI;
129 typedef stack< char > SKC;
130 typedef deque< int > DQI;
131 typedef queue< int > QI;
132 typedef priority_queue< int > PQIMax;
133 typedef priority_queue< int, VI, greater< int > > PQIMin;
134 const double EPS = 1e-8;
135 const LL inf = 0x7fffffff;
136 const LL infLL = 0x7fffffffffffffffLL;
137 const LL mod = 1e9 + 7;
138 const int maxN = 1e5 + 7;
139 const LL ONE = 1;
140 const LL evenBits = 0xaaaaaaaaaaaaaaaa;
141 const LL oddBits = 0x5555555555555555;
142 
143 int solve(int&);
144 
145 int N, ans;
146 string str;
147 
148 // 取得str中从x开始的下一个数,取完之后index指向下一个运算符或右括号的位置 
149 inline int getNextNum(int &idx) {
150     int sgn = 1;
151     string ret;
152     
153     if(str[idx] == '-') {
154         sgn = -sgn; 
155         ++idx;
156     }
157     else if(str[idx] == '(') return solve(++idx);
158     
159     while(str[idx] >= '0' && str[idx] <= '9') ret.PB(str[idx++]);
160     
161     return sgn * toInt(ret);
162 }
163 
164 inline int exec(int x, int y, char op) {
165     if(op == '+') return x + y;
166     if(op == '-') return x - y;
167     if(op == '*') return x * y;
168     if(op == '/') return x / y;
169     assert(false);
170 } 
171  
172 inline int solve(int &idx) {
173     int ret = getNextNum(idx);
174 
175     while(idx < N) {
176         if(str[idx] == ')') {
177             ++idx;
178             return ret;
179         }
180         
181         char op = str[idx++];
182         int tmp = getNextNum(idx);
183         
184         if(op == '+' || op == '-') {
185             while(idx < N && (str[idx] == '*' || str[idx] == '/')) {
186                 tmp = exec(tmp, getNextNum(++idx), str[idx]);
187             }
188         }
189         
190         ret = exec(ret, tmp, op);
191     }
192     
193     return ret;
194 }
195 
196 int main() {
197     //freopen("MyOutput.txt","w",stdout);
198     //freopen("input.txt","r",stdin);
199     INIT();
200     int index = 0;
201     
202     cin >> str;
203     N = str.size();
204     ans = solve(index);
205     cout << ans << endl;
206     return 0;
207 }
View Code

 

posted @ 2019-08-27 16:42  梦樱羽  阅读(304)  评论(0编辑  收藏  举报
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