First Recuring Character
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//Brute force method
function firstRecuringCharacter(input){
for(let i=0;i<input.length;i++){
for(let j=i-1;j>=0;j--){
if(input[j]===input[i]){
return input[i]
}
}
}
return undefined
}
//Optimal Solution using Hash Table
function firstRecuringCharacter1(input){
let map={};
for(let i=0;i<input.length;i++){
if(map[input[i]]!=undefined){
return input[i]
}else{
map[input[i]]=i
}
}
return undefined
}
firstRecuringCharacter1([1,1,3,3])
JavaScript
INFO