374. Guess Number Higher or Lower
Easy
We are playing the Guess Game. The game is as follows:
I pick a number from 1 to n. You have to guess which number I picked.
Every time you guess wrong, I'll tell you whether the number is higher or lower.
You call a pre-defined API guess(int num)
which returns 3 possible results (-1
, 1
, or 0
):
-1 : My number is lower 1 : My number is higher 0 : Congrats! You got it!
Example :
Input: n = 10, pick = 6 Output: 6
package leetcode.easy; /* The guess API is defined in the parent class GuessGame. @param num, your guess @return -1 if my number is lower, 1 if my number is higher, otherwise return 0 int guess(int num); */ class GuessGame { public int guess(int num) { if (6 > num) { return -1; } else if (6 == num) { return 0; } else { return 1; } } } public class GuessNumberHigherOrLower extends GuessGame { public int guessNumber1(int n) { for (int i = 1; i < n; i++) { if (guess(i) == 0) { return i; } } return n; } public int guessNumber2(int n) { int low = 1; int high = n; while (low <= high) { int mid = low + (high - low) / 2; int res = guess(mid); if (res == 0) { return mid; } else if (res < 0) { high = mid - 1; } else { low = mid + 1; } } return -1; } public int guessNumber3(int n) { int low = 1; int high = n; while (low <= high) { int mid1 = low + (high - low) / 3; int mid2 = high - (high - low) / 3; int res1 = guess(mid1); int res2 = guess(mid2); if (res1 == 0) { return mid1; } if (res2 == 0) { return mid2; } else if (res1 < 0) { high = mid1 - 1; } else if (res2 > 0) { low = mid2 + 1; } else { low = mid1 + 1; high = mid2 - 1; } } return -1; } @org.junit.Test public void test() { GuessNumberHigherOrLower guessNumberHigherOrLower = new GuessNumberHigherOrLower(); System.out.println(guessNumberHigherOrLower.guessNumber1(10)); System.out.println(guessNumberHigherOrLower.guessNumber2(10)); System.out.println(guessNumberHigherOrLower.guessNumber3(10)); } }