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O(n) Maximum subarray bugfix and tests #138

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Merged
merged 2 commits into from
Feb 27, 2018
Merged

O(n) Maximum subarray bugfix and tests #138

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1c828f2
Add O(n) maximum subarray test
emyarod Feb 27, 2018
1fe106d
Fix O(n) maximum subarray solution
emyarod Feb 27, 2018
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9 changes: 4 additions & 5 deletions src/searching/maximum-subarray.js
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Original file line number Diff line number Diff line change
Expand Up @@ -20,11 +20,10 @@
* @return {Number} Maximum sum of the elements of a subarray.
*/
function maxSubarray(array) {
var currentMax = 0;
var max = 0;

for (var i = 0; i < array.length; i += 1) {
currentMax = Math.max(0, currentMax + array[i]);
var currentMax = array[0];
var max = array[0];
for (var i = 1; i < array.length; i += 1) {
currentMax = Math.max(array[i], currentMax + array[i]);
max = Math.max(max, currentMax);
}
return max;
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29 changes: 29 additions & 0 deletions test/searching/maximum-subarray.spec.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,29 @@
var maxSubArray = require('../../src/searching/maximum-subarray').maxSubarray;

describe('Maximum subarray', function() {
'use strict';

it('should work with empty arrays', function() {
expect(maxSubArray([])).toBeUndefined();
});

it('should return the only element when an array with single element is passed', function() {
expect(maxSubArray([42])).toBe(42);
});

it('should return the only negative element when an array with single element is passed', function() {
expect(maxSubArray([-42])).toBe(-42);
});

it('should return the zero when an array with single element, which is zero is passed', function() {
expect(maxSubArray([0])).toBe(0);
});

it('should return the max sum of a subarray', function() {
expect(maxSubArray([1, -1, 2, 3, -1])).toBe(5);
});

it('should return the max negative number when array with negative numbers is provided', function() {
expect(maxSubArray([-10, -1, -2, -3, -1])).toBe(-1);
});
});