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754. Reach a Number

Description

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

You can make some number of moves numMoves so that:

• On each move, you can either go left or right.
• During the ith move (starting from i == 1 to i == numMoves), you take i steps in the chosen direction.

Given the integer target, return the minimum number of moves required (i.e., the minimum numMoves) to reach the destination.

 

Example 1:

Input: target = 2
Output: 3
Explanation:
On the 1st move, we step from 0 to 1 (1 step).
On the 2nd move, we step from 1 to -1 (2 steps).
On the 3rd move, we step from -1 to 2 (3 steps).

Example 2:

Input: target = 3
Output: 2
Explanation:
On the 1st move, we step from 0 to 1 (1 step).
On the 2nd move, we step from 1 to 3 (2 steps).

 

Constraints:

• -109 <= target <= 109
• target != 0

Solutions

• Java
• C++
• Python
• Go
• Javascript

• class Solution {
      public int reachNumber(int target) {
          target = Math.abs(target);
          int s = 0, k = 0;
          while (true) {
              if (s >= target && (s - target) % 2 == 0) {
                  return k;
              }
              ++k;
              s += k;
          }
      }
  }
  

• class Solution {
  public:
      int reachNumber(int target) {
          target = abs(target);
          int s = 0, k = 0;
          while (1) {
              if (s >= target && (s - target) % 2 == 0) return k;
              ++k;
              s += k;
          }
      }
  };
  

• class Solution:
      def reachNumber(self, target: int) -> int:
          target = abs(target)
          s = k = 0
          while 1:
              if s >= target and (s - target) % 2 == 0:
                  return k
              k += 1
              s += k
  
  

• func reachNumber(target int) int {
  	if target < 0 {
  		target = -target
  	}
  	var s, k int
  	for {
  		if s >= target && (s-target)%2 == 0 {
  			return k
  		}
  		k++
  		s += k
  	}
  }
  

• /**
   * @param {number} target
   * @return {number}
   */
  var reachNumber = function (target) {
      target = Math.abs(target);
      let [s, k] = [0, 0];
      while (1) {
          if (s >= target && (s - target) % 2 == 0) {
              return k;
          }
          ++k;
          s += k;
      }
  };
  
  

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