754. Reach a Number

You are standing at position 0 on an infinite number line. There is a goal at position target.

On each move, you can either go left or right. During the n-th move (starting from 1), you take n steps.

Return the minimum number of steps required to reach the destination.

Example 1:

Input: target = 3
Output: 2
Explanation:
On the first move we step from 0 to 1.
On the second step we step from 1 to 3.

Example 2:

Input: target = 2
Output: 3
Explanation:
On the first move we step from 0 to 1.
On the second move we step  from 1 to -1.
On the third move we step from -1 to 2.

Note:
target will be a non-zero integer in the range [-10^9, 10^9].
  • Greedy
    • harder than easy

class Solution {
    public int reachNumber(int target) {
        target = Math.abs(target);
        int distance = 0, step = 0;
        while (distance < target) {
            distance += ++step;
        }
        int delta = target - distance;
        if(delta % 2 == 0)
            return step;
        else if((delta + step + 1) % 2 == 0)
            return step + 1;
        else
            return step + 2;
    }
}