ZOJ 1941

无聊题，中缀表达式。一口气写了290行，就如炎炎烈日下当头一兜凉水般的爽快。

 

 

#include <iostream> #include <string> #include <vector> #include <stack> #include <cctype> using namespace std; string str; int cs = 1; int lev ( char c ) { if ( c == '+' || c == '-' ) return 1; if ( c == '*' ) return 2; if ( c == '(' || c == '@' ) return 0; return -1; } void print ( const vector <int> &v ) { int i; for ( i = 0; i < v.size (); i ++ ) { if ( v[i] == -1000 ) printf ( "x" ); else if ( v[i] >= 0 ) printf ( "%d", v[i] ); else printf ( "%c", v[i] + 500 ); } printf ( "/n" ); } void proc () { int i = str.find_first_of ( '=' ); string left = str.substr ( 0, i ); string right = str.substr ( i + 1, str.size () ); left += '@', right += '@'; stack <int> is; stack <int> xs; stack <char> cs; vector <int> iv; int sum = 0; cs.push ( '@' ); for ( i = 0; i < left.size (); i ++ ) { if ( left[i] == 'x' ) { iv.push_back ( -1000 ); } else if ( isdigit ( left[i] ) ) { sum = sum * 10 + left[i] - '0'; if ( !isdigit ( left[i + 1] ) ) { iv.push_back ( sum ); sum = 0; } } else if ( left[i] != '@' ) { if ( left[i] == '(' ) { cs.push ( '(' ); } else if ( left[i] == ')' ) { while ( cs.top () != '(' ) { iv.push_back ( cs.top () - 500 ); cs.pop (); } cs.pop (); } else { char ch = left[i]; if ( lev ( ch ) > lev ( cs.top () ) ) cs.push ( ch ); else { while ( lev ( cs.top () ) >= lev ( ch ) ) { iv.push_back ( cs.top () - 500 ); cs.pop (); } cs.push ( ch ); } } } else { while ( cs.top () != '@' ) { iv.push_back ( cs.top () - 500 ); cs.pop (); } } } int la = 0, lb = 0; // ax = b for ( i = 0; i < iv.size (); i ++ ) { if ( iv[i] >= 0 ) { is.push ( iv[i] ); xs.push ( 0 ); } else if ( iv[i] == -1000 ) { is.push ( 0 ); xs.push ( 1 ); } else { char ch = iv[i] + 500; int a1 = xs.top (); xs.pop (); int a2 = xs.top (); xs.pop (); int b1 = is.top (); is.pop (); int b2 = is.top (); is.pop (); if ( ch == '+' ) { xs.push ( a1 + a2 ); is.push ( b1 + b2 ); } if ( ch == '-' ) { xs.push ( a1 - a2 ); is.push ( b1 - b2 ); } if ( ch == '*' ) { if ( a1 == 0 && a2 == 0 ) xs.push ( 0 ); if ( a1 == 0 && a2 != 0 ) xs.push ( a2 * b1 ); if ( a2 == 0 && a1 != 0 ) xs.push ( a1 * b2 ); is.push ( b1 * b2 ); } } } la = xs.top (); lb = is.top (); xs.pop (); is.pop (); //printf ( "%d %d/n", a, b ); //print ( iv ); iv.clear (); for ( i = 0; i < right.size (); i ++ ) { if ( right[i] == 'x' ) { iv.push_back ( -1000 ); } else if ( isdigit ( right[i] ) ) { sum = sum * 10 + right[i] - '0'; if ( !isdigit ( right[i + 1] ) ) { iv.push_back ( sum ); sum = 0; } } else if ( right[i] != '@' ) { if ( right[i] == '(' ) { cs.push ( '(' ); } else if ( right[i] == ')' ) { while ( cs.top () != '(' ) { iv.push_back ( cs.top () - 500 ); cs.pop (); } cs.pop (); } else { char ch = right[i]; if ( lev ( ch ) > lev ( cs.top () ) ) cs.push ( ch ); else { while ( lev ( cs.top () ) >= lev ( ch ) ) { iv.push_back ( cs.top () - 500 ); cs.pop (); } cs.push ( ch ); } } } else { while ( cs.top () != '@' ) { iv.push_back ( cs.top () - 500 ); cs.pop (); } } } int ra = 0, rb = 0; // ax = b for ( i = 0; i < iv.size (); i ++ ) { if ( iv[i] >= 0 ) { is.push ( iv[i] ); xs.push ( 0 ); } else if ( iv[i] == -1000 ) { is.push ( 0 ); xs.push ( 1 ); } else { char ch = iv[i] + 500; int a1 = xs.top (); xs.pop (); int a2 = xs.top (); xs.pop (); int b1 = is.top (); is.pop (); int b2 = is.top (); is.pop (); if ( ch == '+' ) { xs.push ( a1 + a2 ); is.push ( b1 + b2 ); } if ( ch == '-' ) { xs.push ( a1 - a2 ); is.push ( b1 - b2 ); } if ( ch == '*' ) { if ( a1 == 0 && a2 == 0 ) xs.push ( 0 ); if ( a1 == 0 && a2 != 0 ) xs.push ( a2 * b1 ); if ( a2 == 0 && a1 != 0 ) xs.push ( a1 * b2 ); is.push ( b1 * b2 ); } } } ra = xs.top (); rb = is.top (); xs.pop (); is.pop (); //printf ( "%d %d/n", la, lb ); //printf ( "%d %d/n", ra, rb ); int a = la - ra, b = rb - lb; if ( a == 0 && b == 0 ) printf ( "Infinitely many solutions./n" ); else if ( a == 0 && b != 0 ) printf ( "No solution./n" ); else printf ( "x = %f/n", double ( b ) / double ( a ) ); } int main () { //freopen ( "in.txt", "r", stdin ); while ( getline ( cin, str ) ) { printf ( "Equation #%d/n", cs ++ ); proc (); printf ( "/n" ); } return 0; }