Get the first missing positive integer

README.md

Search Missing Integer in a given array of Integers

For eg.

1. searchMissingPositiveInteger([1,4,123]) // should give 2
2. searchMissingPositiveInteger([-12, -3]) // should give 1
3. searchMissingPositiveInteger([1, 2, ... , 999]) // should give 1000

search-missing-positive-integer.js

function makeHashmap(array) { // create hash map out of array
	var hash = {};
	array.reduce(function (next, value) {
		return hash[value] = value;
	}, hash);
	return hash;
}

function searchMissingPositiveInteger(arrOfIntegers) {
    var sortedArrOfIntergers = arrOfIntegers.sort(function(a, b){return a-b});
    var totalLength = sortedArrOfIntergers.length;
    var lastInteger = sortedArrOfIntergers[totalLength - 1];
    if (lastInteger < 0) return 1; // return 1 if the last integer is negative
    var hashOfIt = makeHashmap(sortedArrOfIntergers); // create hash of array for O(N) complexity
    for (var i = 1; i <= lastInteger; i++) {
        if(!hashOfIt[i]) return i; // search for not existing integer in the hash
    }
    return lastInteger + 1; // add 1 to last integer if couldn't find the missing positive integer
}