Sort numbers from 1..n in time complexity::o(n) and space complexity o(1).

sort.java

int []arr = new int[]{2,1,4,1,4};
        for(int i=0;i<arr.length; i++) {
            if(arr[i] > 0) {
                int elementIndex = arr[i] - 1;
                if (arr[elementIndex] > 0) {
                    arr[i] = arr[elementIndex];
                    arr[elementIndex] = -1;
                    i--;
                } else {
                    arr[elementIndex]--;
                    arr[i] = 0;
                }
            }
        }

        for(int i=0;i<arr.length;i++) {
            System.out.println("Count of "+(i+1) + " is "+Math.abs(arr[i]));
        }