折腾二维数组

#include<iostream>using namespace std ;int main (){    int i,j,k;    int a[5][4]= {{0,1},{4,5},{8,9},{12,13},{16,17}};    cout<<"请输入后两列的10个元素："<<endl;    for(i=0; i<5; ++i)        for(j=2; j<=3; ++j)            cin>>a[i][j];    cout<<"数组中元素的值为："<<endl;    for(i=0; i<5; ++i)    {        cout<<"第"<<i<<"行:";        for(j=0; j<4; ++j)            cout<<a[i][j]<<"   ";        cout<<endl;    }    cout<<"现在将所有元素乘以3倍。。。完成！"<<endl;    for(i=0; i<5; ++i)    {        for(j=0; j<4; ++j)            a[i][j]*=3;    }    cout<<"按行序优先输出："<<endl;    for(i=0; i<5; ++i)    {        cout<<"第"<<i<<"行：" ;        for(j=0; j<4; ++j)            cout<<a[i][j]<<'\t';        cout<<endl;    }    cout<<"按列序优先输出:"<<endl;    for(j=0; j<4; ++j)    {        cout<<"第"<<j<<"列: ";        for(i=0; i<5; ++i)            cout<<a[i][j]<<'\t';        cout<<endl;    }    cout<<"将数组倒着输出："<<endl;    for(i=4; i>=0; --i)    {        cout<<"第"<<i<<"行: ";        for(j=3; j>=0; --j)            cout<<a[i][j]<<'\t';        cout<<endl;    }    cout<<"输出数组中所有偶数："<<endl;    for(i=0; i<5; ++i)    {        for(j=0; j<4; ++j)            if(a[i][j]%2==0)                cout<<"a["<<i<<"]["<<j<<"]="<<a[i][j]<<'\t';        cout<<endl;    }    cout<<"行列下标之和为3的倍数的值 :"<< endl;    for(i=0; i<5; ++i)    {        for(j=0; j<4; ++j)        {            k=i+j;            if(k%3==0)            {                cout<<"a["<<i<<"]["<<j<<"]="<<a[i][j]<<'\t';                cout<<endl;            }        }    }    return 0;}