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binary-search.js
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binary-search.js
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var A = [1,2,3,4,5,6,6,6,7,8,9];
console.log(BinarySearch(A, 2));
console.log(BinarySearchRecursive(A, 0, A.length, 6));
console.log(BinarySearchFirstLast(A, 6, 'last'));
console.log(BinaryCountOccurances(A, 6));
function BinarySearch(A, item) {
var start = 0;
var end = A.length-1;
var mid;
while (start <= end) {
mid = Math.floor((start+end)/2);
if(item == A[mid]) {
return mid;
} else if (item <= A[mid]) {
end = mid-1;
} else {
start = mid + 1;
}
}
return false;
}
function BinarySearchRecursive(A, start, end, item) {
var mid = Math.floor((start+end)/2);
if(item == A[mid]) {
return mid;
} else if (item <= A[mid]) {
return BinarySearchRecursive(A, start, mid-1, item);
} else {
return BinarySearchRecursive(A, mid+1, end, item);
}
return false;
}
function BinarySearchFirstLast(A, item, firstOrLast) {
var start = 0;
var end = A.length-1;
var mid;
var result = -1;
while (start <= end) {
mid = Math.floor((start+end)/2);
if(item == A[mid]) {
result = mid;
if (firstOrLast === 'first')
end = mid - 1;
else if (firstOrLast === 'last')
start = mid + 1;
} else if (item < A[mid]) {
end = mid-1;
} else {
start = mid + 1;
}
}
return result;
}
function BinaryCountOccurances(A, item) {
var firstIndex = BinarySearchFirstLast(A, item, "first");
var lastIndex;
var result;
if(firstIndex === -1) {
return 0;
}
lastIndex = BinarySearchFirstLast(A, item, "last");
if(lastIndex === -1){
return -1;
}
return lastIndex - firstIndex +1;
}