算法总结之 最大值减去最小值或等于num的子数组数量

Posted 2020-10-06

给定数组arr和整数num，共返回有多少个子数组满足  <= num

 

数组长度N    时间复杂度O(N)

package TT;

import java.util.LinkedList;

public class Test127 {
 
	  public int getNum(int[] arr, int num){
		  if(arr==null || arr.length == 0){
			  return 0;
		  }
		  LinkedList<Integer> qmin = new LinkedList<Integer>();
		  LinkedList<Integer> qmax = new LinkedList<Integer>();
		  int i = 0;
		  int j = 0;
		  int res = 0;
		  while(i<arr.length){
			  while(j<arr.length){
			  while(!qmin.isEmpty() && arr[qmin.peekLast()]>=arr[j]){
				   qmin.pollLast();
			  }
			  qmin.addLast(j);
			  
			  while(!qmax.isEmpty() && arr[qmax.peekLast()]<=arr[j]){
				  qmax.pollLast();
			  }
			  
			  qmax.addLast(j);
			 
			  if(arr[qmax.getFirst()]-arr[qmin.getFirst()]>num){
				  break;
			  }
			  j++;
		  }
		  if(qmin.peekFirst()==i){
			  qmin.pollFirst();
		  }
		  if(qmax.peekFirst()==i){
			  qmax.pollFirst();
		  }
		  
		  res += j-i;
		  i++;
		  }
		  return res;
	  }
	
	
}