Evaluate expressions (one of the applications in the data structure book stack)

Main Content: evaluate the expression, submit nyoj to pass...

The idea is to open two stacks, one operator stack, and the other operator stack ..

My code is as follows (relatively simple ):

/***** Author gery ******/# include <iostream> # include <cstdio> # include <cstring> # include <algorithm> # include <map> # include <vector> # include <cmath> # include <string> # include <stack> # include <queue> # define EPS 1e-9 # define ll long # define INF 0x3f3f3fusing namespace std; const int maxn = 1000 + 10; stack <double> LY; stack <char> gery; char STR [maxn], OP [maxn]; char operation [7] [7] // operator priority {'>', '>', '<', '> ', '>'}, // '+' {'>', '>', '<', '>', '> '}, // '-' {'>', '>', '<', '>', '> '}, // '*' {'>', '>', '<', '>', '> '}, // '/' {'<', '<', '= ',','}, // '(' {'>', '> '},//') '{' <',' <',', '='}, // '= '}; int get_index (char ch) {Switch (CH) {Case '+': Return 0; Case '-': return 1; Case '*': return 2; case '/': return 3; Case '(': return 4; Case ')': return 5; Case '=': return 6 ;}} char get_prio (char, char B) {int c = get_index (a); int d = get_index (B); return operation [C] [d];} double cal_value (double A, double B, char c) {Switch (c) {Case '+': Return A + B; Case '-': return a-B; Case '*': return a * B; case '/': return a * 1.0/B;} int main () {int T, PD, CNT, I; double temp, left_value, right_value, Val; char CH, OP; scanf ("% d", & T); While (t --) {scanf ("% s", STR); ly. empty (); Gery. empty (); Gery. push ('='); for (I = 0; I <strlen (STR); I ++) {CNT = 0, Pd = I; // Pd is the character pointer if (isdigit (STR [I]) | STR [I] = '. '| STR [I] ='-') // The number of rounds. {While (isdigit (STR [Pd]) | STR [Pd] = '. '| STR [Pd] ='-') {op [CNT] = STR [Pd]; CNT ++, PD ++ ;} OP [CNT] = '\ 0'; temp = atof (OP); // the system function is short for ASCII to float, similar to atoi, is to convert the string to the Float Type Function ly. push (temp); I = pd-1;} else {CH = get_prio (Gery. top (), STR [I]); Switch (CH) {case' <': Gery. push (STR [I]); break; Case '=': Gery. pop (); break; Case '>': op = Gery. top (), Gery. pop (); right_value = ly. top (), Ly. pop (); left_value = ly. top (), Ly. pop (); val = cal_value (left_value, right_value, OP); ly. push (VAL); I --; break; // After expression operation, the character pointer must be moved back }}} printf ("%. 2lf \ n ", Ly. top ();} return 0;}/* 2 (-2 + 3) * 1.2 + 2) = (-2 + 3) * 10/2) = */

Later, AC saw other people use the method in the book to perform the sub-assembly, but it was too troublesome to know which method is better...

Evaluate expressions (one of the applications in the data structure book stack)