Replace succeeding number with zero using if statement

I have these result set using loop condition and would output the following:

 |    50,000  |
 |    50,000  |
 |    50,000  |
 |   100,000  |
 |   100,000  |
 |   300,000  |
 |   300,000  |

What i would like to happen is change the succeeding number to zero (0),showing only unique values like:

 |    50,000  |
 |         0  |
 |         0  |
 |   100,000  |
 |         0  |
 |   300,000  |
 |         0  |

How can i achieve this one using if else statement?