#7209 adding prefixsum algorithms by adding two java files prefixsum.java and prefixsum1.java

Author: mahalaxmidasari18

src/main/java/com/thealgorithms/prefixsum/prefixsum.java

@@ -0,0 +1,28 @@
+package com.thealgorithms.prefixsum;
+
+class prefixsum {
+    int[] prefix;
+    public prefixsum(int[] nums) {
+        int n = nums.length;
+        prefix = new int[n];
+        int cur = 0;
+        for (int i = 0; i < n; i++) {
+            cur += nums[i];
+            prefix[i] = cur;
+        }
+    }
+    public int sumRange(int left, int right) {
+        if (left == 0) {
+            return prefix[right];
+        } else {
+            return prefix[right] - prefix[left - 1];
+        }
+    }
+
+    public static void main(String[] args) {
+        int[] nums = { 1, 2, 3, 4 };
+        prefixsum obj = new prefixsum(nums);
+        System.out.println(obj.sumRange(0, 2)); 
+        System.out.println(obj.sumRange(1, 3)); 
+    }
+}

src/main/java/com/thealgorithms/prefixsum/prefixsum1.java

@@ -0,0 +1,24 @@
+package com.thealgorithms.prefixsum;
+
+class Solution {
+    public int minSubArrayLen(int target, int[] nums) {
+        int currentsum = 0;
+        int low = 0;
+        int high = 0;
+
+        int minlenwindow = Integer.MAX_VALUE;
+
+        for (high = 0; high < nums.length; high++) {
+            currentsum += nums[high];
+
+            while (currentsum >= target) {
+                int currentwindow = high - low + 1;
+                minlenwindow = Math.min(minlenwindow, currentwindow);
+                currentsum = currentsum - nums[low];
+                low++;
+            }
+        }
+
+        return minlenwindow == Integer.MAX_VALUE ? 0 : minlenwindow;
+    }
+}