# 题目

You are given two arrays (without duplicates) nums1 and nums2 where nums1’s elements are subset of nums2. Find all the next greater numbers for nums1's elements in the corresponding places of nums2.

The Next Greater Number of a number x in nums1 is the first greater number to its right in nums2. If it does not exist, output -1 for this number.

Example 1:

Input: nums1 = [4,1,2], nums2 = [1,3,4,2].
Output: [-1,3,-1]
Explanation:
For number 4 in the first array, you cannot find the next greater number for it in the second array, so output -1.
For number 1 in the first array, the next greater number for it in the second array is 3.
For number 2 in the first array, there is no next greater number for it in the second array, so output -1.

Example 2:

Input: nums1 = [2,4], nums2 = [1,2,3,4].
Output: [3,-1]
Explanation:
For number 2 in the first array, the next greater number for it in the second array is 3.
For number 4 in the first array, there is no next greater number for it in the second array, so output -1.

Note:

1. All elements in nums1 and nums2 are unique.
2. The length of both nums1 and nums2 would not exceed 1000.

# 思路

## 题目大意：

1. nums1与nums2中的所有元素都是唯一的。
2. nums1与nums2的元素个数不超过1000。

# 代码

nextGreaterElement.go

``````package _496_Next_Greater_Element_I

func NextGreaterElement(findNums []int, nums []int) []int {
var ret []int
var numsMap map[int]int

numsLen := len(nums)

numsMap = make(map[int]int, numsLen)

for i := 0; i < numsLen; i++ {
numsMap[nums[i]] = i
}

findNumsLen := len(findNums)
for i := 0; i < findNumsLen; i++ {
num := findNums[i]
pos, _ := numsMap[num]

var ok bool
for j := pos; j < numsLen; j++ {
if nums[j] > num {
ret = append(ret, nums[j])
ok = true
break
}
}
if !ok {
ret = append(ret, -1)
}
}

return ret
}
``````

## 测试代码

nextGreaterElement_test.go

``````package _496_Next_Greater_Element_I

import "testing"

func isSliceEqual(ret, want []int) bool {
len1 := len(ret)
len2 := len(want)

if len1 != len2 {
return false
}

for i := 0; i < len1; i++ {
if ret[i] != want[i] {
return false
}
}

return true
}
func TestNextGreaterElement(t *testing.T) {
nums1, nums2 := []int{4,1,2}, []int{1,3,4,2}
want := []int{-1,3,-1}

ret := NextGreaterElement(nums1, nums2)

if isSliceEqual(ret, want) {
t.Logf("pass")
} else {
t.Errorf("fail, want %+v, get %+v", want, ret)
}
}

func TestNextGreaterElement2(t *testing.T) {
nums1, nums2 := []int{2,4}, []int{1,2,3,4}
want := []int{3,-1}

ret := NextGreaterElement(nums1, nums2)

if isSliceEqual(ret, want) {
t.Logf("pass")
} else {
t.Errorf("fail, want %+v, get %+v", want, ret)
}
}
``````
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