Merge pull request #110 from nicolefffe/js-binary-search

issue #86 - add binary search algorithm for javascript

Author: danielabrozzoni

Algorithms/Searching Algorithms/Binary Search/Javascript/BinarySearch.js

@@ -0,0 +1,55 @@
+// can execute script with Node.js (v6) by running: node BinarySearch.js
+
+const generateArray = (length, multiplier) => {
+    let arr = [];
+    for (i = 1; i <= length; i++) {
+        arr.push(i * multiplier);
+    }
+    return arr;
+};
+
+const binarySearch = (arr, valueToFind) => {
+    let min = 0;
+    let max = arr.length - 1;
+    let iterations = 0;
+    let searchIndex, found;
+
+    while (max >= min) {
+        // start by looking at value in middle of array (assuming it is sorted)
+        searchIndex = Math.floor((max + min) / 2);
+        foundValue = arr[searchIndex];
+        iterations++;
+
+        if (foundValue === valueToFind) {
+            break;
+        }
+        // on each iteration, reduce search range by half by:
+        // adjusting min if midway value was less than search value, or
+        // adjusting max if midway value was greater than search value
+        min = foundValue < valueToFind ? searchIndex + 1 : min;
+        max = foundValue > valueToFind ? searchIndex - 1 : max;
+    }
+    foundValue = foundValue === valueToFind ? valueToFind : -1;
+    return {
+        foundValue,
+        searchIndex,
+        iterations
+    };
+};
+
+const main = () => {
+    const arr = generateArray(Math.ceil(Math.random() * 100), Math.ceil(Math.random() * 10));
+    console.log(`Array is: [ ${arr.join(', ')} ]`);
+
+    const value = Math.ceil(Math.random() * 100);
+    console.log(`Will attempt to find ${value} in array.`);
+
+    const { foundValue, iterations, searchIndex } = binarySearch(arr, value);
+    if (foundValue === -1) {
+        console.log(`Did not find value in ${iterations} iterations.`)
+    } else {
+        console.log(`Found ${foundValue} at index ${searchIndex} after ${iterations} iterations.`)
+    }
+};
+
+main();