367. Valid Perfect Square Java Solutions

Given a positive integer num, write a function which returns True if num is a perfect square else False.

Note:do no built-in library function such as sqrt .

Example 1:

Input:16returns:true

Example 2:

Input:14returns:false

Credits:
Special thanks to @elmirap for adding this problem and creating all test cases.

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Solution One:

1  Public classSolution {2      Public BooleanIsperfectsquare (intnum) {3         if(Num < 0)return false;4         if(num = = 1)return true;5          for(inti = 1; i<= num/i;i++){6             if(i*i = = num)return true;7         }8         return false;9     }Ten}

Solution 2: Binary Lookup method (Java without AC for reference only)

1  Public classSolution {2      Public BooleanIsperfectsquare (intnum) {3         if(Num < 0)return false;4         if(num = = 1)return true;5         intLow = 0, high = NUM/2;6          while(Low <=High ) {7             LongMid = (low + high)/2;8             LongTMP = mid*mid;9             if(tmp = = num)return true;Ten             if(tmp > num) high = Mid-1; One             ElseLow = mid + 1; A         } -         return false; -     } the}

The solution 3:https://leetcode.com/discuss/110659/o-1-time-c-solution-inspired-by-q_rsqrt the O (1) Solution of the Great God.

Solution 4:

The total number of squares is a series of odd sum, for example:

1 = 1
4 = 1 + 3
9 = 1 + 3 + 5
16 = 1 + 3 + 5 + 7
25 = 1 + 3 + 5 + 7 + 9
36 = 1 + 3 + 5 + 7 + 9 + 11
....
1+3+...+ (2n-1) = (2n-1 + 1)N/2 =n

1  Public classSolution {2      Public BooleanIsperfectsquare (intnum) {3         inti = 1;4          while(num > 0) {5num-=i;6i + = 2;7         }8         returnnum = = 0;9     }Ten}

367. Valid Perfect Square Java Solutions