Doubt doubt doubt

#1

kya is question ke liye Hashmap aana jaroori h ???

pre [sum]++; —> iska kya matlab h ???

#2

memset kya h ???

#3

hello @parth_tyagi

function hai jo array ko 0 aur -1 se initialise karta hai.

aata hai tab achi baat hai ,uske bina bhi ho jayega

sum ko as indexing treat kar rahe hai aur us index pe jo value hai usko 1 se badha rahe hai