What is the different between a[i 1] and a[i] ?-CodePudding

I am not able to understand why both values are different and how does it change?

int a[100]

for(int i=0; i<100; i  )
cin >> a[i];

int i=20;

cout << a[i 1] << endl;
cout << a[i]  ;

I tried to know value of both

CodePudding user response：

a[i 1] that means value of i 1th index. which means, lets suppose if i=20 and it has value of 50 and a[21] has value of 200 then a[i 1] means a[i 1]=200 so when it's about a[i 1] then it point to the next and a[i] that means increase 1 by ith index value. so i=20 and a[i]=50 and a[i] means 50 1 which is 51

CodePudding user response：

When you declare this int a[100], it contains 100 zeroes.

In the for-loop, those 100 zeroes are output.

Even after assigning i manually to 20, a[20 1] still contains the value zero. The expression a[i] is actually increasing the value of the index 20 by saying a[20] = a[20] 1

CodePudding user response：

a[i 1] you just accessing  the index of i 1  ; 
example : 
you have an array 
[4,5,6,7] and i = 0 ; 
cout<<arr[i 1] 
means than you want to print arr[0 1] which have value 5 : 
[4,5,6,7]
   ^
but when you do arr[i]   that means that you modify the value of 4 to 
become 5 
in case if arr[i]   simply you just add  1 to the value in arr[i]