UVa 465 - Overflow

来源：互联网发布：js截取小数点后两位编辑：程序博客网时间：2024/05/21 15:48

题目：给你一个计算式（2个操作数，一个运算符），问操作数和结果是否溢出。

分析：模拟。转换成大数运算，然后分别把每个数字转化成整型，看是否相同即可。

注意：<cstring>库中没有strrev；输出的原数字的前导0不要丢掉。

#include <iostream>#include <cstdlib>#include <string.h>#include <cstdio>using namespace std;char a[10000],b[10000],c[10000],d[10000];int  a_buf[10000],b_buf[10000],c_buf[10000];int over_flow( char* s ){//去除前导0 char buf[10000];int len = strlen(s),now = 0;while ( now+1 < len && s[now] == '0' )now ++;strcpy( buf, &s[now] );int value = 0;for ( int i = 0 ; buf[i] ; ++ i ) {value *= 10;value += buf[i]-'0';}char A[10000],B[10000];int count = 0;while ( !count || value ) {A[count ++] = value%10 + '0';value /= 10;}int times = 0;while ( count )B[times ++] = A[-- count];B[times] = 0; return strcmp( buf, B );}void plu( char* d, char* a, char* b ){memset( a_buf, 0, sizeof( a_buf ) );memset( b_buf, 0, sizeof( b_buf ) );memset( c_buf, 0, sizeof( c_buf ) );int l_a = strlen(a),l_b = strlen(b);int len = max(l_a, l_b )+1;for ( int i = 0 ; i < l_a ; ++ i )a_buf[i] = a[l_a-1-i]-'0';for ( int i = 0 ; i < l_b ; ++ i )b_buf[i] = b[l_b-1-i]-'0';for ( int i = 0 ; i < len ; ++ i ) {c_buf[i] += a_buf[i] + b_buf[i];if ( c_buf[i] > 9 ) {c_buf[i+1] ++;c_buf[i] -= 10;}}while ( len > 0 && !c_buf[len] ) -- len;for ( int i = 0 ; i <= len ; ++ i )d[i] = c_buf[len-i]+'0';d[len+1] = 0;}void mul( char* d, char* a, char* b ){memset( a_buf, 0, sizeof( a_buf ) );memset( b_buf, 0, sizeof( b_buf ) );memset( c_buf, 0, sizeof( c_buf ) );int l_a = strlen(a),l_b = strlen(b);int len = l_a*l_b+1;for ( int i = 0 ; i < l_a ; ++ i )a_buf[i] = a[l_a-1-i]-'0';for ( int i = 0 ; i < l_b ; ++ i )b_buf[i] = b[l_b-1-i]-'0';for ( int i = 0 ; i < l_a ; ++ i ) for ( int j = 0 ; j < l_b ; ++ j )c_buf[i+j] += a_buf[i] * b_buf[j];for ( int i = 0 ; i < len ; ++ i )if ( c_buf[i] > 9 ) {c_buf[i+1] += c_buf[i]/10;c_buf[i] %= 10;}while ( len > 0 && !c_buf[len] ) -- len;for ( int i = 0 ; i <= len ; ++ i )d[i] = c_buf[len-i]+'0';d[len+1] = 0;}int main(){while ( cin >> a >> c >> b ) {cout << a << " " << c << " " << b << endl;if ( over_flow(a) )cout << "first number too big" << endl;if ( over_flow(b) )cout << "second number too big" << endl;if ( c[0] == '+' ) plu( d, a, b );if ( c[0] == '*' ) mul( d, a, b );if ( over_flow(d) )cout << "result too big" << endl;}return 0;}

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