Difficulty: Easy
More:【目录】LeetCode Java实现
Description
https://leetcode.com/problems/sum-of-square-numbers/submissions/
Given a non-negative integer c, your task is to decide whether there're two integers aand b such that a2 + b2 = c.
Example 1:
Input: 5
Output: True
Explanation: 1 * 1 + 2 * 2 = 5
Example 2:
Input: 3
Output: False
Intuition
Using two pointers: One starts from the beginning, the other starts from the end.
It's very similar to Two Sum II - Input array is sorted
Solution
public boolean judgeSquareSum(int c) {
int i=0, j=(int)Math.sqrt(c);
while(i<=j){
int ans=i*i+j*j;
if(ans<c){
i++;
}else if(ans>c){
j--;
}else{
return true;
}
}
return false;
}
Complexity
Time complexity : O(n)
Space complexity : O(1)
What I've learned
1.The use of two pointers.
More:【目录】LeetCode Java实现