Time: 216 ms (100%), Space: 86.9 MB (100%) - LeetHub

Author: furic

3727-maximum-alternating-sum-of-squares/3727-maximum-alternating-sum-of-squares.ts

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+const maxAlternatingSum = (nums: number[]): number => {
+    // Key insight: Since we square all values, signs don't matter - use absolute values
+    const absoluteValues = nums.map(Math.abs);
+    absoluteValues.sort((a, b) => a - b);
+    
+    const arrayLength = absoluteValues.length;
+    let maxScore = 0n;
+
+    // Greedy strategy: Pair largest with smallest to maximize (large² - small²)
+    // Process pairs from both ends moving inward
+    const pairCount = Math.floor(arrayLength / 2);
+    
+    for (let pairIndex = 0; pairIndex < pairCount; pairIndex++) {
+        const largestValue = BigInt(absoluteValues[arrayLength - pairIndex - 1]);
+        const smallestValue = BigInt(absoluteValues[pairIndex]);
+        
+        // Add difference: large² - small²
+        const pairContribution = largestValue * largestValue - smallestValue * smallestValue;
+        maxScore += pairContribution;
+    }
+
+    // If odd number of elements, add the middle element squared (no pair to subtract)
+    if (arrayLength % 2 === 1) {
+        const middleIndex = Math.floor(arrayLength / 2);
+        const middleValue = BigInt(absoluteValues[middleIndex]);
+        maxScore += middleValue * middleValue;
+    }
+
+    return Number(maxScore);
+};