Return -1 if target is not in array (#9)

* return -1 if target is not in array

* return -1 if target is not in array (python)

* <= in binary search while loop

utilities/javascript/binarySearch.js

@@ -1,7 +1,7 @@
 function binarySearch(arr, target) {
     let left = 0;
     let right = arr.length - 1;
-    while (left < right) {
+    while (left <= right) {
         let mid = left + Math.floor((right - left) / 2);
         if (arr[mid] === target) {
             return mid;
@@ -12,15 +12,15 @@ function binarySearch(arr, target) {
             right = mid - 1;
         }
     }
-    return left;
+    return -1;
 }
 
 console.log(binarySearch([1, 2, 3, 10], 1) === 0)
 console.log(binarySearch([1, 2, 3, 10], 2) === 1)
 console.log(binarySearch([1, 2, 3, 10], 3) === 2)
 console.log(binarySearch([1, 2, 3, 10], 10) === 3)
-console.log(binarySearch([1, 2, 3, 10], 9) === 3)
-console.log(binarySearch([1, 2, 3, 10], 4) === 3)
-console.log(binarySearch([1, 2, 3, 10], 0) === 0)
-console.log(binarySearch([1, 2, 3, 10], 11) === 3)
-console.log(binarySearch([5, 7, 8, 10], 3) === 0)
+console.log(binarySearch([1, 2, 3, 10], 9) === -1)
+console.log(binarySearch([1, 2, 3, 10], 4) === -1)
+console.log(binarySearch([1, 2, 3, 10], 0) === -1)
+console.log(binarySearch([1, 2, 3, 10], 11) === -1)
+console.log(binarySearch([5, 7, 8, 10], 3) === -1)

utilities/python/binary_search.py

@@ -1,7 +1,7 @@
 def binary_search(arr, target):
     left = 0;
     right = len(arr) - 1
-    while left < right:
+    while left <= right:
         mid = left + (right - left) // 2;
         if arr[mid] == target:
             return mid
@@ -9,14 +9,14 @@ def binary_search(arr, target):
             left = mid + 1
         else:
             right = mid - 1
-    return left
+    return -1
 
 print(binary_search([1, 2, 3, 10], 1) == 0)
 print(binary_search([1, 2, 3, 10], 2) == 1)
 print(binary_search([1, 2, 3, 10], 3) == 2)
 print(binary_search([1, 2, 3, 10], 10) == 3)
-print(binary_search([1, 2, 3, 10], 9) == 3)
-print(binary_search([1, 2, 3, 10], 4) == 3)
-print(binary_search([1, 2, 3, 10], 0) == 0)
-print(binary_search([1, 2, 3, 10], 11) == 3)
-print(binary_search([5, 7, 8, 10], 3) == 0)
+print(binary_search([1, 2, 3, 10], 9) == -1)
+print(binary_search([1, 2, 3, 10], 4) == -1)
+print(binary_search([1, 2, 3, 10], 0) == -1)
+print(binary_search([1, 2, 3, 10], 11) == -1)
+print(binary_search([5, 7, 8, 10], 3) == -1)