假设数组定义为：
int arr[5] = {1,2,3,4,5};
for(int i=0; i<=5; i++) cout << arr[i] << " ";
for(int i=0; i<5; i++) cout << arr[i] << " ";
for(int i=1; i<=5; i++) cout << arr[i] << " ";
int i=0; while(i<5) cout << arr[i] << " ";