leetcode 219. Contains Duplicate II

題目

Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the difference between i and j is at most k.

解1(超時)

public class Solution {
     public boolean containsNearbyDuplicate(int[] nums, int k) {

         if(k<1||nums.length<2||nums==null) 
            return false;

         for(int i=0;i<nums.length-1-k;i++){
            for(int j=1;j<=k;j++){
                if(nums[i]==nums[i+j]){
                    return true;
                }
            }
         }

         return false;
     }
}

解2

public class Solution {
    public boolean containsNearbyDuplicate(int[] nums, int k) {  
        if(nums==null || nums.length<2) return false;  
        //key=int, val=index  
        Map<Integer, Integer> map = new HashMap<Integer, Integer>();  
        for(int i=0; i<nums.length; i++) {  
            if(map.containsKey(nums[i])) {  
                int j = map.get(nums[i]);  
                if(i-j<=k) 
                   return true; 
                else{
                     map.remove(nums[j]);
                     map.put(nums[i], i);
                }
            } else {
                map.put(nums[i], i);
            }  
        }  
        return false;  
    }  
}

參考鏈接

http://blog.csdn.net/xudli/article/details/46236267