Algorithm to reverse a string.
Step1 : start
Step2 : Take two variable i and j
Step3 : do length (string)-1, to set J at last position
Step4 : do string [0], to set i on the first character.
Step5 : string [i] is interchanged with string[j]
Step6 : Increment i by 1
Step7 : Increment j by 1
Step8 : if i>j then go to step3
Step9 : Stop
