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# 06/05/2022 1299. Replace Elements with Greatest Element on Right Side

Method: scan the loop from the end. set max = -1 first. use tmp to get the current value, set arr\[i] to max and get the max by comparing tmp and current max value.

Time O(n) Space O(1)

```
// Some code
class Solution {
    public int[] replaceElements(int[] arr) {
        int max = -1;
        for (int i = arr.length - 1; i >= 0; i--){
            int tmp = arr[i];
            arr[i] = max;
            max = Math.max(max, tmp)
            
        }
        return arr;
    }
}
```