checkIfPairInArrayHaveASum

const arr1 = [1,3,4,5];
const arr2 = [1,3,4,4];
const asum = 9

// neive approach 
const isSumAvailable1 = (arr,sum) => {
    for (i=0; i<arr.length;i++){
        for (j=i+1; j<arr.length;j++){
            if(arr[j]+arr[i] == sum) return true;
        }
    }
    return false;
} 

const isSumAbailable2 = (arr,sum) => {
    const aSet = new Set();
    for (i=0; i<arr.length;i++){
        if(aSet.has(arr[i])) return true;
        aSet.add(sum - arr[i])
    }
    return false
}

console.log(isSumAbailable2(arr1,asum));
console.log(isSumAbailable2(arr2,asum));