add 1664 ts solution

JeremyXXXuuu · JeremyXXXuuu · commit 7db4c63fafbe · 2023-03-02T11:13:42.000+01:00
diff --git a/Problems/27-Ways-to-Make-a-Fair-Array/1664.ts b/Problems/27-Ways-to-Make-a-Fair-Array/1664.ts
@@ -0,0 +1,25 @@
+function waysToMakeFair(nums: number[]): number {
+  const n: number = nums.length;
+  nums.unshift(0);
+  let leftEven: number[] = new Array(n + 1).fill(0);
+  let leftOdd: number[] = new Array(n + 1).fill(0);
+  let leftEvenSum = 0,
+    leftOddSum = 0;
+  for (let i = 1; i <= n; i++) {
+    if (i % 2 === 0) leftEvenSum += nums[i];
+    else leftOddSum += nums[i];
+    leftEven[i] = leftEvenSum;
+    leftOdd[i] = leftOddSum;
+  }
+  let rightEvenSum = 0,
+    rightOddSum = 0;
+  let res = 0;
+  for (let i = n; i >= 1; i--) {
+    if (leftEven[i - 1] + rightOddSum === leftOdd[i - 1] + rightEvenSum) {
+      res++;
+    }
+    if (i % 2 === 0) rightEvenSum += nums[i];
+    else rightOddSum += nums[i];
+  }
+  return res;
+}
