题目:
Given an array of integers and an integer k, find out whether there 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.
分析:
这道题目考察的是数组的操作,给定一个数组和一个整数k,要求判断数组元素在k步返回内时候有重复元素,采用双层for循环的话时间复杂度是O(nk),k=n,n-1,n-2…如果采用hashmap,算法时间复杂度则降为O(n).
代码:
import java.util.HashMap;
import java.util.Map;
public class ContainsDuplicate {
public static boolean containsNearbyDuplicate2(int[] nums, int k) {
if(nums==null || nums.length<2) return false;
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;
}
map.put(nums[i],i);
}
return false;
}
public static void main(String[] args){
int[] a={0,2,3,-1,2,2};
boolean result=containsNearbyDuplicate2(a,1);
System.out.println("result:"+result);
}
}