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

Author: a93a

Diff for: kotlin/0303-range-sum-query-immutable.kt

@@ -0,0 +1,25 @@
+class NumArray(nums: IntArray) {
+
+    val prefix = IntArray(nums.size)
+
+    init {
+        var sum = 0
+        for((i,v) in nums.withIndex()) {
+            sum += v
+            prefix[i] = sum
+        }
+    }
+
+    fun sumRange(left: Int, right: Int): Int {        
+        val prefixR = prefix[right]
+        val prefixL = if(left == 0) 0 else prefix[left - 1]
+        return prefixR - prefixL
+    }
+
+}
+
+/**
+ * Your NumArray object will be instantiated and called as such:
+ * var obj = NumArray(nums)
+ * var param_1 = obj.sumRange(left,right)
+ */