/**
* Problem : https://leetcode.com/problems/circular-array-loop/submissions/
* Time Complexity : O(n)
* Space Complexity : O(1)
*/
public class CircularArrayLoop {
public boolean circularArrayLoop(int[] nums) {
int N = nums.length;
int K = 1001;
for (int i=0; i1000 || nums[i]<-1000)
continue;
boolean direction = (nums[i]>0);
int ix=i;
int nextIndex;
while (true) {
nextIndex = getNextIndex(nums, ix);
if(
(nums[nextIndex]>1000 && nums[nextIndex]!=K) || (nums[nextIndex]<-1000 && nums[nextIndex]!=-K) ||
nextIndex==ix || nums[nextIndex]>0)!=direction {
break;
}
if(nums[nextIndex]==(direction?K:-K)){
return true;
}
nums[ix] = (direction?K:-K);
ix = nextIndex;
}
K+=1;
}
return false;
}
private int getNextIndex(int[] nums, int i) {
int N = nums.length;
int out = (nums[i] + i)%N;
return (out>=0)?out:(out+N);
}
}