Create 0303-range-sum-query-immutable.swift

Author: drxlx

swift/0303-range-sum-query-immutable.swift

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+/**
+ * Question Link: https://leetcode.com/problems/range-sum-query-immutable/
+ */
+
+
+class NumArray {
+    var pref: [Int]
+
+    init(_ nums: [Int]) {
+        pref = []
+        var total = 0
+        for n in nums {
+            total += n
+            pref.append(total)
+        }
+    }
+    
+    func sumRange(_ left: Int, _ right: Int) -> Int {
+        let prefRight = pref[right]
+        let prefLeft = left > 0 ? pref[left - 1] : 0
+        return (prefRight - prefLeft)
+    }
+}
+
+/**
+ * Your NumArray object will be instantiated and called as such:
+ * let obj = NumArray(nums)
+ * let ret_1: Int = obj.sumRange(left, right)
+ */