一个c++函数的问题？

#include<iostream>
#include<algorithm>
using namespace std;
string big(int a[]){
    int b[]={4};
    int k=sizeof(a)/sizeof(int);
    reverse(a,a+5);//反转 
    int re[7];
    int j=0;
    for(int i=0;i<k;i++){
        re[i+j]=a[i]*b[j];//相乘 
    }
    for(int i=0;i<6;i++){
        if(re[i]>9){
            re[i+1]=re[i+1]+re[i]/10;
            re[i] %= 10;//进位 
        }    
    }
    if(re[5]==0){
        static string str1,str2,str3,str4,str5,str6;
        str1= re[0]+'0';
        str2= re[1]+'0';
        str3= re[2]+'0';
        str4= re[3]+'0';
        str5= re[4]+'0';
        str6=str1+str2+str3+str4+str5;
        return str6;
    }
    else{
        static string str1,str2,str3,str4,str5,str6,str7;
        str1= re[0]+'0';
        str2= re[1]+'0';
        str3= re[2]+'0';
        str4= re[3]+'0';
        str5= re[4]+'0';
        str6= re[5]+'0';
        str7=str1+str2+str3+str4+str5+str6;
        return str7;
    }    
}
int main(){
    int a[5]={1,2,3,4,5};
    string g=big(a);
    cout<<g;
}

函数调用结果错误（单独使用函数可以用）

int re[7];
但a只有5个元素，那么在函数中并没有给re[5]和re[6]赋值啊，会是一个随机值，怎么会有正确的结果呢
试试a[7]吧

供参考：

#include<iostream>
#include<algorithm>
using namespace std;
string big(int a[]) {
    int b[] = { 4 };
    int k = 5;
    cout<<sizeof(a) / sizeof(int)<<endl;
    reverse(a, a + 5);//反转 
    for (int i = 0; i < k; i++)
        cout << a[i]<<" ";
    cout << endl;
    int re[7] = {0};
    int j = 0;
    for (int i = 0; i < k; i++) {
        re[i + j] = a[i] * b[j];//相乘 
    }
    for (int i = 0; i < 6; i++) {
        if (re[i] > 9) {
            re[i + 1] = re[i + 1] + re[i] / 10;
            re[i] %= 10;//进位 
        }
    }
    if (re[5] == 0) {
        static string str1, str2, str3, str4, str5, str6;
        str1 = re[0] + '0';
        str2 = re[1] + '0';
        str3 = re[2] + '0';
        str4 = re[3] + '0';
        str5 = re[4] + '0';
        str6 = str1 + str2 + str3 + str4 + str5;
        return str6;
    }
    else {
        static string str1, str2, str3, str4, str5, str6, str7;
        str1 = re[0] + '0';
        str2 = re[1] + '0';
        str3 = re[2] + '0';
        str4 = re[3] + '0';
        str5 = re[4] + '0';
        str6 = re[5] + '0';
        str7 = str1 + str2 + str3 + str4 + str5 + str6;
        return str7;
    }
}
int main() {
    int a[5] = { 1,2,3,4,5 };
    string g = big(a);
    cout << g;
}