Answers

2016-01-11T20:50:15+05:30
In an array msg[ ], msg[i+1] represents the value given to the index (i+1) of the array. 
msg[i]+1 takes the value stored in index i and adds 1 to it.
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2016-01-13T23:18:52+05:30
Msg[i+1] means the index of array increase by 1
msg[i]+1 means the value at that index should increase by 1
1 5 1