Product //大数相乘

客官°小女子只卖身不卖艺 2022-08-06 00:28 120阅读 0赞

#include <stdio.h>
    #include <string.h>
    
    #define N 1000
    void yiwei(char *ch, int a);
    void add(char *ch1, char *ch2);
    void rev(char *ch);
    
    int main()
    {
        char ch1[N], ch2[N], ch3[N], ch4[N];
    	int i, j, k;
    
        while(scanf("%s %s", ch1, ch2) != -1)
        {
            rev(ch1);rev(ch2);
            memset(ch4, 0, sizeof(ch4));
    
            for( i=0; ch1[i]!=0; i++)
            {
                memset(ch3, 0, sizeof(ch3));
                for( j=0; ch2[j]!=0; j++)       //ch3中存的是对应位乘积+1，不加1可能为0了。
                {
                    ch3[j] =  (ch1[i]-'0')*(ch2[j]-'0')+1;
                }
                for( k=0; ch3[k]; k++)
                {
                    if(ch3[k]-1 > 9)
                    {
    					if(!ch3[k+1])
    					{
    						ch3[k+1] += (ch3[k]-1)/10+1;
    						ch3[k] = (ch3[k]-1)%10+1;
    					}
    					else
    					{
    						ch3[k+1] += (ch3[k]-1)/10;
    						ch3[k] = (ch3[k]-1)%10+1;
    					}
                    }
               } 
    			k = 0;
    			 while(ch3[k])
    			 {	
    				 ch3[k] = ch3[k]-1+'0';	
    				 k++;
    			 }
                yiwei(ch3, i);
                add(ch4, ch3);
            }
    
            rev(ch4);
    
    		if(ch4[0]=='0')
    			ch4[1] = 0;
    
            printf("%s\n", ch4);
        }
        return 0;
    }
    void yiwei(char *ch, int a)
    {
        int len, i;
        len = strlen(ch);
        for( i=len+a; i>=a; i--)
        {
            ch[i] = ch[i-a];
        }
        for(i=0; i<a; i++)
            ch[i] = '0';
    }
    void add(char *ch1, char *ch2)
    {
        int i = 0;
        while(ch1[i] || ch2[i])
        {
            if(!ch1[i] || !ch2[i])
                ch1[i] = ch1[i]+ch2[i];
            else
                ch1[i] = ch1[i]+ch2[i]-'0';
    		i++;
        }
        i = 0;
        while(ch1[i])
        {
            if(ch1[i] > '9')
            {
                if(!ch1[i+1])
                {
                    ch1[i+1] += (ch1[i]-'0')/10+'0';
                    ch1[i] = '0'+(ch1[i]-'0')%10;
                }
                else
                {
                    ch1[i+1] += (ch1[i]-'0')/10;
                    ch1[i] = '0'+(ch1[i]-'0')%10;
                }
            }
    		i++;
        }
    }
    void rev(char *ch)
    {
    	int len, i;
    	char ch1[N];
    	len = strlen(ch);
    	for(i=0; i<len; i++)
    		ch1[len-i-1] = ch[i];
    	for(i=0; i<len; i++)
    		ch[i] = ch1[i];
    }