Create 3351-sum-of-good-subsequences.js

Author: everthis

3351-sum-of-good-subsequences.js

@@ -0,0 +1,29 @@
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var sumOfGoodSubsequences = function (nums) {
+    const mod = 1000000007n;
+    const MAX = 100005;
+    const sum = new Array(MAX).fill(0n);
+    const cnt = new Array(MAX).fill(0n);
+
+    for (let i = nums.length - 1; i >= 0; i--) {
+        const v = nums[i];
+        cnt[v]++;
+
+        const tmp = 1n + cnt[v + 1] + (cnt[v - 1] || 0n);
+        cnt[v] += cnt[v + 1];
+        cnt[v] += cnt[v - 1] || 0n;
+
+        sum[v] += BigInt(v) * tmp;
+
+        sum[v] += sum[v + 1];
+        sum[v] += sum[v - 1] || 0n;
+
+        cnt[v] %= mod;
+        sum[v] %= mod;
+    }
+
+    return Number(sum.reduce((a, b) => (a + b) % mod, 0n));
+}