689

Author: lazzzis

689/Solution.java

@@ -0,0 +1,63 @@
+class Solution {
+    public int[] maxSumOfThreeSubarrays(int[] nums, int k) {
+        Node[] lefts = new Node[nums.length];
+        int[] subSums = new int[nums.length];
+        int tempSum = 0;
+        for (int i = 0; i < k; i++) {
+            tempSum += nums[i];
+        }
+        int maxVal = tempSum;
+        int maxValId = 0;
+        lefts[0] = new Node(tempSum, 0);
+        subSums[0] = tempSum;
+        for (int i = 1; i < nums.length - k; i++) {
+            tempSum = tempSum - nums[i - 1] + nums[i + k - 1];
+            if (maxVal < tempSum) {
+                maxVal = tempSum;
+                maxValId = i;
+            }
+            subSums[i] = tempSum;
+            lefts[i] = new Node(maxVal, maxValId);
+        }
+        Node[] rights = new Node[nums.length];
+        tempSum = 0;
+        for (int i = nums.length - 1; i >= nums.length - k; i--) {
+            tempSum += nums[i];
+        }
+        rights[nums.length - k] = new Node(tempSum, nums.length - k);
+        maxVal = tempSum;
+        maxValId = nums.length - k;
+        for (int i = nums.length - k - 1; i >= 0; i--) {
+            tempSum = tempSum + nums[i] - nums[i + k];
+            if (maxVal <= tempSum) {
+                maxVal = tempSum;
+                maxValId = i;
+            }
+            rights[i] = new Node(maxVal, maxValId);
+        }
+        maxVal = 0;
+        int[] res = new int[3];
+        for (int i = k; i <= nums.length - k * 2; i++) {
+            if (subSums[i] + lefts[i - k].value + rights[i + k].value > maxVal) {
+                maxVal = subSums[i] + lefts[i - k].value + rights[i + k].value;
+                res[0] = lefts[i - k].index;
+                res[1] = i;
+                res[2] = rights[i + k].index;
+            }
+        }
+        return res;
+    }
+
+    class Node {
+        int value;
+        int index;
+
+        public Node() {
+        }
+
+        public Node(int value, int index) {
+            this.value = value;
+            this.index = index;
+        }
+    }
+}

689/main.js

@@ -0,0 +1,56 @@
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number[]}
+ */
+var maxSumOfThreeSubarrays = function(nums, k) {
+  const lefts = new Array(nums.length)
+  const rights = new Array(nums.length)
+  const sumOfSubArr = new Array(nums.length).fill(0)
+
+  for (let i = 0; i < k; i++) {
+    sumOfSubArr[0] += nums[i]
+  }
+  for (let i = 1; i <= nums.length - k; i++) {
+    sumOfSubArr[i] = sumOfSubArr[i - 1] + nums[i + k - 1] - nums[i - 1]
+  }
+
+  let maxSumOfSubArr = 0
+  let idOfMaxSumOfSubAtt = 0
+  for (let i = 0; i <= nums.length - k; i++) {
+    if (maxSumOfSubArr < sumOfSubArr[i]) {
+      maxSumOfSubArr = sumOfSubArr[i]
+      idOfMaxSumOfSubAtt = i
+    }
+    lefts[i] = idOfMaxSumOfSubAtt
+  }
+
+  idOfMaxSumOfSubAtt = nums.length - k
+  maxSumOfSubArr = 0
+  for (let i = nums.length - k; i >= 0; i--) {
+    if (maxSumOfSubArr <= sumOfSubArr[i]) {
+      maxSumOfSubArr = sumOfSubArr[i]
+      idOfMaxSumOfSubAtt = i
+    }
+    rights[i] = idOfMaxSumOfSubAtt
+  }
+
+  maxSumOfSubArr = 0
+  let ans = new Array(3)
+  for (let i = k; i <= nums.length - 2 * k; i++) {
+    const leftId = lefts[i - k]
+    const rightId = rights[i + k]
+    if (maxSumOfSubArr <= sumOfSubArr[leftId] + sumOfSubArr[i] + sumOfSubArr[rightId]) {
+      maxSumOfSubArr = sumOfSubArr[leftId] + sumOfSubArr[i] + sumOfSubArr[rightId]
+      ans = [leftId, i, rightId]
+    }
+  }
+  return ans
+};
+
+if (process.env.LZS) {
+  const assert = require('chai').assert
+  assert.deepStrictEqual(maxSumOfThreeSubarrays([1,2,1,2,6,7,5,1], 2), [0, 3, 5])
+  assert.deepStrictEqual(maxSumOfThreeSubarrays([4, 5, 10, 6, 11, 17, 4, 11, 1, 3], 1), [4, 5, 7])
+  assert.deepStrictEqual(maxSumOfThreeSubarrays([7,13,20,19,19,2,10,1,1,19], 3), [1, 4, 7])
+}

README.md

@@ -126,6 +126,7 @@
 - [681 Next Closest Time](./681)
 - [682 Baseball Game](./682)
 - [684 Redundant Connection](./684)
+- [689 Maximum Sum of 3 Non-Overlapping Subarrays](./689)
 
 *Q: What is `LZS`? It almost appears inside all files (like js, cpp)?*
 A: Briefly speaking, that is an environment variable defined in my System. For unix/linux, you can add a command `export LZS='true'` in `~/.bashrc` such that `process.env.LZS` evaluates to `true` rather than `undefined.`