MoveAllZerosToEnd.java

    //If the given arrays is {1, 9, 8, 4, 0, 0, 2, 7, 0, 6, 0}
    //,it should be changed to {1, 9, 8, 4, 2, 7, 6, 0, 0, 0, 0}. 
    //The order of all other elements should be same. 
    //Expected time complexity is O(n) and extra space is O(1).

    public static void swap (int a[],int start,int end) {
        int tmp = a[start];
        a[start] = a[end];
        a[end] = tmp;
    }

    /**
     * Idea : 1.Count # of Non zero elements
     * 	      2.Insert zero after the non zero elements
     * @param a
     */
    public static void moveAllZerosToEnd (int a[]) {
        int end = a.length;
        int cnt = 0;
        for (int i=0;i < end;i++) {
            if (a[i] != 0) {
                swap(a,i,cnt);
                cnt++;
            }
        }
//        while (cnt < end) {
//            a[cnt++] = 0;
//        }
        for (int i=0;i<a.length;i++) {
            System.out.print(a[i] + "," );
        }
        System.out.println();
    }

    
    public static void main(String[] args) {
        int a[] = {1, 9, 8, 4, 0, 0, 2, 7, 0, 6, 0};
        moveAllZerosToEnd (a);
    }