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package leetcode;

import java.util.*;

public class leetcode503 {

public static void main(String[] args) {

new leetcode503().nextGreaterElements(

new int[]{

1,2,1

}

);

}

//贪心法相对简单

public int[] nextGreaterElements(int[] nums) {

int res[]=new int[nums.length];

Arrays.fill(res,-1);

for (int i = 0; i <nums.length ; i++) {

for (int j=i;j<nums.length;j++){

if (nums[i]<nums[j]){

res[i]=nums[j];

break;

}

if (j==nums.length-1){

for (int k = 0; k <i ; k++) {

if (nums[i]<nums[k]){

res[i]=nums[k];

break;

}

if (k==i-1){

res[i]=-1;

}

}

}

}

}

return res;

}

//单调栈

public int[] SnextGreaterElements(int[] nums) {

Deque<Integer> stack = new ArrayDeque<>();

int len = nums.length;

int[] res = new int[len];

Arrays.fill(res, -1);

for (int i = 0; i < 2 * len; i++) {

int num = nums[(i+len) % len]; //关键步骤

while (!stack.isEmpty() && num > nums[stack.peek()]) {

res[stack.pop()] = num;

}

// use for second round

if (i < len) stack.push(i);

if (stack.isEmpty()) break;

}

return res;

}

}