leetcode 219. Contains Duplicate II

题目

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(超时)

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;
}
}

参考链接

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