Create 1524-number-of-sub-arrays-with-odd-sum.js

Author: everthis

1524-number-of-sub-arrays-with-odd-sum.js

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+/**
+ * @param {number[]} arr
+ * @return {number}
+ */
+const numOfSubarrays = function(arr) {
+  const n = arr.length, mod = 1e9 + 7
+
+  let oc = 0, ec = 1
+  let sum = 0
+  let res = 0
+  for(let i = 0; i < n; i++) {
+    sum += arr[i]
+    if(sum % 2 === 1) {
+      res += ec
+      oc++
+    } else {
+      res += oc
+      ec++
+    }
+  }
+  
+  return res % mod
+};