Create 457-circular-array-loop.js

Author: everthis

457-circular-array-loop.js

@@ -0,0 +1,39 @@
+/**
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+const circularArrayLoop = function(nums) {
+    let n = nums.length;
+    for (let i = 0; i < n; i++) {
+        if (nums[i] == 0) {
+            continue;
+        }
+        let j = i, k = getIndex(i, nums);
+        while (nums[k] * nums[i] > 0 && nums[getIndex(k, nums)] * nums[i] > 0) {
+            if (j === k) {
+                // check for loop with only one element
+                if (j === getIndex(j, nums)) {
+                    break;
+                }
+                return true;
+            }
+            j = getIndex(j, nums);
+            k = getIndex(getIndex(k, nums), nums);
+        }
+        // loop not found, set all element along the way to 0
+        j = i;
+        let val = nums[i];
+        while (nums[j] * val > 0) {
+            let next = getIndex(j, nums);
+            nums[j] = 0;
+            j = next;
+        }
+    }
+    return false;
+};
+
+    
+function getIndex(i, nums) {
+    const n = nums.length;
+    return i + nums[i] >= 0? (i + nums[i]) % n: n + ((i + nums[i]) % n);
+}