求助

_lyc @ 2023-07-17 20:25:53

#include <iostream>
#include <cstring>
using namespace std;
const int MAXN = 2e3+10;
int a[MAXN],b[MAXN],ans[MAXN*2],len1,len2,cnt;
char num1[MAXN],num2[MAXN];
int main(){
    cin>>num1>>num2;
    len1 = strlen(num1),len2 = strlen(num2),cnt = len1+len2;
    for(int i = len1-1,j = 1;i >= 0;i--,j++) a[j] = num1[i] - '0';
    for(int i = len2-1,j = 1;i >= 0;i--,j++) b[j] = num2[i] - '0';
    for(int i = 1;i <= len1;i++)
        for(int j = 1;j <= len2;j++) ans[i+j-1] += a[i]*b[j];
    for(int i = 1;i <= len1+len2;i++){
        ans[i+1] += ans[i]/10;
        ans[i] %= 10;
    }
    while(!ans[cnt]) cnt--;
    for(int i = cnt;i >= 1;i--) cout<<ans[i];
    return 0;
}

by Minecraftmine @ 2023-07-17 20:35:32

 while(!ans[cnt]) cnt--;

改成

 while(ans[cnt]==0 && cnt>1) cnt--;

by Minecraftmine @ 2023-07-17 20:36:27

@lyc0613

by bookchong @ 2023-07-17 20:49:10

你应该加个特判。如果num1或者num2为0，则最后的答案为0.所以如果num1或num2为0，直接输出0即可

所以在main函数中添加

if(num1 == "0" || num2 == "0") cout << 0 << endl;

就行

完整代码（我把你用的char改成了string）

#include <iostream>
#include <cstring>
using namespace std;
const int MAXN = 2e3+10;
int a[MAXN],b[MAXN],ans[MAXN*2],len1,len2,cnt;
string num1,num2;
int main(){
    cin>>num1>>num2;
    if(num1 == "0" || num2 == "0") cout << 0 << endl;
    len1 = num1.size(),len2 = num2.size(),cnt = len1+len2;
    for(int i = len1-1,j = 1;i >= 0;i--,j++) a[j] = num1[i] - '0';
    for(int i = len2-1,j = 1;i >= 0;i--,j++) b[j] = num2[i] - '0';
    for(int i = 1;i <= len1;i++)
        for(int j = 1;j <= len2;j++) ans[i+j-1] += a[i]*b[j];
    for(int i = 1;i <= len1+len2;i++){
        ans[i+1] += ans[i]/10;
        ans[i] %= 10;
    }
    while(!ans[cnt]) cnt--;
    for(int i = cnt;i >= 1;i--) cout<<ans[i];
    return 0;
}

by _lyc @ 2023-07-17 20:51:07

@Minecraftmine @Sun09426 已AC，感谢神犇