大整数相减

#include<stdio.h>#include<string.h>#include<stdlib.h>#include<assert.h>char* bigIntMinus( const char* numstr1, const char* numstr2 ){        assert( numstr1 != NULL && numstr2 != NULL );        int len1 = strlen( numstr1 );        int len2 = strlen( numstr2 );        int resultLen = ( len1 > len2 ) ? ( len1 + 2 ) : ( len2 + 2 );        char* minusResult = new char[ resultLen ];        bool bFirstIsBigger = true;        // 首先处理结果符号        if ( len1 > len2 )        {                *minusResult = '+';        }        else if ( len1 < len2 )        {                *minusResult = '-';                bFirstIsBigger = false;        }        else        {                int cmpResult = strcmp( numstr1, numstr2 );                if ( cmpResult > 0 )                {                        *minusResult = '+';                }                else                {                        *minusResult = '-';                        bFirstIsBigger = false;                }        }        int tmpBigger[ resultLen ];        int tmpSmaller[ resultLen ];        int tmpResult[ resultLen ];        memset( tmpBigger, 0, resultLen * sizeof( int ) );        memset( tmpSmaller, 0, resultLen * sizeof( int ) );        memset( tmpResult, 0, resultLen * sizeof( int ) );        int i, j, k;        if ( bFirstIsBigger )        {                for ( i = 0; i < len1; i++ )                {                        tmpBigger[ i ] = *( numstr1 + len1 - i - 1 ) - '0';                }                for ( j = 0; j < len2; j++ )                {                        tmpSmaller[ j ] = *(numstr2 + len2 - j - 1 ) - '0';                }        }        else        {                for ( i = 0; i < len2; i++ )                {                        tmpBigger[ i ] = *( numstr2 + len2 - i - 1 ) - '0';                }                for ( j = 0; j < len1; j++ )                {                        tmpSmaller[ j ] = *( numstr1 + len1 -j -1 ) - '0';                }        }        // 求差        int currMINUS = 0;        for ( k = 0; k < resultLen; k++ )        {                currMINUS = tmpBigger[ k ] - tmpSmaller[ k ];                if ( currMINUS >= 0 )                {                        tmpResult[ k+1 ] = currMINUS;                }                else // 当前相减为负                {                        tmpBigger[ k+1 ] -= 1; // 高位借位                        tmpResult[ k+1 ] = 10 + currMINUS;                }        }        k = resultLen -1;        while( !tmpResult[ k ] )        {                k--;        }        for ( i = 0; i <= k; i++ )        {                *( minusResult + i + 1 ) = tmpResult[ k-i ] + '0';        }        *( minusResult + i ) = '\0';        return minusResult;}int main(){        const char* str1 = "198345793";        const char* str2 = "4943094930439340493039472";        char* result = bigIntMinus( str1, str2 );        printf( "%s - %s = %s\n", str1, str2, result );        // delete        delete[] result;        return 0;}

// main output

kennie@cbib:~/cplusplus$ g++ -o bigIntMinus.out bigIntMinus.cppkennie@cbib:~/cplusplus$ ./bigIntMinus.out198345793 - 4943094930439340493039472 = -4943094930439340294693679