48 lines
1.3 KiB
Markdown
48 lines
1.3 KiB
Markdown
---
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title: Maximum subarray
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tags: algorithm,math,array
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author: chalarangelo
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cover: work-hard-computer
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firstSeen: 2022-09-07T05:00:00-04:00
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---
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Finds a contiguous subarray with the largest sum within an array of numbers.
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- Use a greedy approach to keep track of the current `sum` and the current maximum, `maxSum`. Set `maxSum` to `-Infinity` to make sure that the highest negative value is returned, if all values are negative.
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- Define variables to keep track of the maximum start index, `sMax`, maximum end index, `eMax` and current start index, `s`.
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- Use `Array.prototype.forEach()` to iterate over the values and add the current value to the `sum`.
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- If the current `sum` is greater than `maxSum`, update the index values and the `maxSum`.
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- If the `sum` is below `0`, reset it to `0` and update the value of `s` to the next index.
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- Use `Array.prototype.slice()` to return the subarray indicated by the index variables.
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```js
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const maxSubarray = (...arr) => {
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let maxSum = -Infinity,
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sum = 0;
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let sMax = 0,
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eMax = arr.length - 1,
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s = 0;
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arr.forEach((n, i) => {
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sum += n;
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if (maxSum < sum) {
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maxSum = sum;
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sMax = s;
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eMax = i;
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}
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if (sum < 0) {
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sum = 0;
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s = i + 1;
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}
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});
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return arr.slice(sMax, eMax + 1);
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};
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```
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```js
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maxSubarray(-2, 1, -3, 4, -1, 2, 1, -5, 4); // [4, -1, 2, 1]
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```
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