[go language questions] go from 0 to entry 4: advanced usage of slice, elementary review and introduction to map

Preface

• This period is for learning Golang Of ： Advanced usage and elementary review of slicing 、Map、 Introduction to conditional and circular statements , If you don't understand something, you can comment and discuss it ！
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Q1： section - Out of the team

Problem description ： The students all lined up , There is a slice showing the height of the corresponding students , Now people who randomly call a certain position are out of the team , Return to the slice after leaving the team . such as [2,3,4,5], The index for 1 Out of line at , After leaving the team, the slices were [2,4,5]

Related knowledge ：
1、s|n| section s The index position is n The item
2、s|:| From slice s Index position of 0 To len(s)-1 Slices obtained at
3、s|low:| From slice s Index position of low To len(s)-1 Slices obtained at
4、s|:high| From slice s Index position of 0 To high Slices obtained at ,len=high
5、s|low: high| From slice s The prime reference position of Iow To high Slices obtained at ,len-high-low
6、s|low: high:max| From slice s The prime reference position of low To high Slices obtained at ,len-high-low, cap=max-low

Sample input ：[1,2,3,4,5,6],3
Sample output ：[1,2,3,5,6]

Case code ：

//import "fmt"
/** *  The class name in the code 、 Method name 、 The parameter name has been specified , Do not modify , Return the value specified by the method directly  * @param s int Integer one-dimensional array   height  * @param index int integer   Out of line index  * @return int Integer one-dimensional array  */
func deleteElement(s []int, index int) []int {
    
	// write code here
	s1 := s[0 : index]
	s2 := s[index+1:]
	s1 = append(s1, s2...)
	return s1
}

Q2： Slice traversal - Judges rate

Problem description ： Xiao Ming takes part in a singing competition , The judges will rate , Ask to remove the highest score , And the lowest score , Save the highest score and the lowest score into the slice and return .

Related knowledge ：
1、int64 Maximum , minimum value , Size comparison , Multiple return values
2、golang The maximum signed value in is math.MaxInt64, The minimum value is math.MinInt64
3、 There are two ways to traverse slices ,for Circulation and for range loop

Sample input ：[1,2,3,4,5,6,7,8,9]
Sample output ：[1,9]

Case code ：

func minAndMax(s []int) []int {
    
	// write code here
	var ans []int
	var a int = s[0]
	var b int = s[0]
	for _, j := range s {
    
		a = max(a, j)
		b = min(b, j)
	}
	ans = append(ans, b)
	ans = append(ans, a)
    return ans
}
func min(a int, b int) int {
    
	if a < b {
    
		return a
	}
	return b
}
func max(a int, b int) int {
    
	if a > b {
    
		return a
	}
	return b
}

Q3： Slice traversal - Adjust the order

Problem description ： The children stood in a row in turn , Now we need to change their order , Reverse row , Stand on the far left from the rightmost person , The person on the penultimate right stands in the second position on the leftmost side , And so on . For example, the order of children is [1,3,2,3,4,6], Rearranged as [6,4,3,2,3,1].

Related knowledge ：
1、len(slice) Find the length of a slice
2、for Loop through slices
3、 The multiple assignment feature makes it easy to exchange variables , Variable one , Variable two ：= Variable two , Variable one

Sample input ：[1,2,3,4,5,6,7,8,9]
Sample output ：[9,8,7,6,5,4,3,2,1]

Case code ：

//import "fmt"
/** *  The class name in the code 、 Method name 、 The parameter name has been specified , Do not modify , Return the value specified by the method directly  * @param s int Integer one-dimensional array  * @return int Integer one-dimensional array  */
func convert(s []int) []int {
    
	// write code here
	length := len(s)
	for i := 0; i < length/2; i++{
    
		s[i], s[length-i-1] = s[length-i-1], s[i]
// tmp := s[i]
// s[i] = s[length-i-1]
// s[length-i-1] = tmp
	}
	return s
}

Q4： Slice traversal - Determine whether two slices have the same elements

Problem description ： Given two slices , Determine whether the elements in the two slices are exactly the same .

Related knowledge ：
1、len(slice) Find the length of a slice
2、for Loop through slices

Sample input ：[1,2,3,4],[1,2,3,4]
Sample output ：true

Case code ：

//import "fmt"

/** *  The class name in the code 、 Method name 、 The parameter name has been specified , Do not modify , Return the value specified by the method directly  * @param s1 int Integer one-dimensional array  * @param s2 int Integer one-dimensional array  * @return bool Boolean type  */
func equal( s1 []int ,  s2 []int ) bool {
    
	// write code here
	length := len(s1)
	for i := 0; i < length; i++{
    
		if s1[i] != s2[i]{
    
			return false
		}
	}
	return true
}

Q5： Merge ordered arrays

Problem description ： Here are two buttons Non decreasing order Array of arranged integers nums1 and nums2, There are two other integers m and n , respectively nums1 and nums2 The number of elements in . Would you please Merge nums2 To nums1 in , Make the merged array press Non decreasing order array . Be careful ： Final , The merged array should not be returned by the function , It's stored in an array nums1 in . In response to this situation ,nums1 The initial length of is m + n, The top m Elements represent the elements that should be merged , after n Elements are 0 , It should be ignored .nums2 The length of is n .

Related knowledge ：
1、for loop
2、break Break the loop
3、append Addition of slices

Sample input ：[1,2,3,0,0,0],3,[2,5,6],3
Sample output ：[1,2,2,3,5,6]

Case code ：

//import "fmt"
/** *  The class name in the code 、 Method name 、 The parameter name has been specified , Do not modify , Return the value specified by the method directly  * @param nums1 int Integer one-dimensional array  * @param m int integer  * @param nums2 int Integer one-dimensional array  * @param n int integer  * @return int Integer one-dimensional array  */

func merge(nums1 []int, m int, nums2 []int, n int) []int {
    
	// write code here
	// similar   Merge sort   From the back   Start judging   Put the big one   return 
	i := m + n - 1
	p1 := m - 1
	p2 := n - 1
	for p1 >= 0 && p2 >= 0 {
    
		if nums1[p1] >= nums2[p2] {
    
			nums1[i] = nums1[p1]
			p1--
			i--
		} else {
    
			nums1[i] = nums2[p2]
			p2--
			i--
		}
	}
	for p1 >= 0 {
    
		nums1[i] = nums1[p1]
		p1--
		i--
	}
	for p2 >= 0 {
    
		nums1[i] = nums2[p2]
		p2--
		i--
	}
	return nums1
}

Q6：Map- League tables

Problem description ： A university dormitory 6 People's math scores are Xiao Ming ：60, Xiao Wang ：70, Zhang San ：95, Li Si ：98, Wang Wu ：100, Zhang Wei ：88 , Now I want to enter the scores of the six students into the score sheet , This grade sheet uses a map To express , The key of the grade sheet is the name of the dormitory member , The value is the corresponding fraction . Print the grade sheet

Related knowledge ：
1、map Statement of ：map[KeyType]ValueType KeyType: Represents the type of key .ValueType: Represents the type of value corresponding to the key .map The default initial value of a variable of type is nil, Need to use make() Function to allocate memory . The grammar is ：make(map[KeyType]ValueType, [cap]) among cap Express map The capacity of , This parameter is not required , But we should be initializing map When the time for its designated a suitable capacity .
2、map[key]=value To assign to key Assign a designated value

Sample input ：
Sample output ：map[ Xiao Ming :60 Xiao Wang :70 Zhang San :95 Zhang Wei :88 Li Si :98 Wang Wu :100]

Case code ：

import "fmt"
func main() {
    
	m1 := make(map[string]int)
	m1[" Xiao Ming "] = 60
	m1[" Xiao Wang "] = 70
	m1[" Zhang San "] = 95
    m1[" Zhang Wei "] = 88
	m1[" Li Si "] = 98
	m1[" Wang Wu "] = 100
	fmt.Println(m1)
}

Q7：Map- Word characters

Problem description ： Given a string consisting only of letters and numbers ,, Count the number of occurrences of each character , And returns the most frequently occurring character .

Related knowledge ：
1、 The elements that make up each string are called “ character ”, You can get the character by traversing or getting a single string element . The characters are in single quotation marks （’） Wrap it up , Such as ：var a = ‘ in ’
2、map Each key Is the only one. .
3、map Statement of ：map[KeyType]ValueType KeyType: Represents the type of key .ValueType: Represents the type of value corresponding to the key .map The default initial value of a variable of type is nil, Need to use make() Function to allocate memory . The grammar is ：make(map[KeyType]ValueType, [cap]) among cap Express map The capacity of , This parameter is not required , But we should be initializing map When the time for its designated a suitable capacity .

Sample input ：“yyds”
Sample output ：y

Case code ：

//import "fmt"
/** *  The class name in the code 、 Method name 、 The parameter name has been specified , Do not modify , Return the value specified by the method directly  * @param s string character string  * @return char Character  */
func character(s string) byte {
    
	// write code here
	arr := ([]byte)(s)
	count := 0
	var ans byte
	charaMap := make(map[byte]int)
	for _, j := range arr {
    

		charaMap[j]++
		if charaMap[j] > count {
    
			count = charaMap[j]
			ans = j
		}
	}
	return ans
}

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