LeetCode Weekly Contest 39

Given a non-negative integer c, your task is to decide whether there're two integers a and b such that a2 + b2 = c.

public class Solution {
    public boolean judgeSquareSum(int c) {
         if(c == 0) return true;
         int left = 0 , right = (int)Math.sqrt(c); //需要18ms，如果是用自己的算法，是12ms
        //  int mid ,temp = 0;
        //  while(temp == 0){
        //      mid = (left + right) / 2;
        //      if(mid > c / mid) {
        //          right = mid - 1;
        //      } else{
        //          if((mid + 1) > c / (mid + 1))
        //             temp = mid;
        //          left = mid + 1;
        //      }
        //  }
        //  right= temp;
        //  left = 0 ;
         while(left <= right){
             int m = left * left + right * right;
             if( m > c) right--;
             else {
                 if(m == c) return true;
                 left++;
             }
         }
         
         return false;
         
    }
}

这种类型的题目肯定是逃不了一个值一个值的试验，所以不要从纯数学的角度考虑怎么解题，而是考虑如果降低时间复杂度。1、缩小遍历范围  2、利用二分查找算法