查找未排序数组中元素的开始和结束索引
原文:https://www . geesforgeks . org/find-start-end-index-element-unsorted-array/
给定一个整数数组，任务是找到给定键的开始和结束位置。
示例:
Input : arr[] = {1, 2, 3, 4, 5, 5}
Key = 5
Output : Start index: 4
Last index: 5
Explanation: Starting index where 5
is present is 4 and ending address is 5.
Input :arr[] = {1, 3, 7, 8, 6},
Key = 2
Output : Key not present in array
Input :arr[] = {1, 8, 7, 8, 6},
Key = 7
Output : Only one occurrence of
key is present at index 2
我们从头开始遍历数组，找到第一个匹配项。如果元素存在，那么我们也从头到尾遍历以查找最后一次出现。
C++
// CPP program to find starting and ending
// indexes of repeated numbers in an array
#include <iostream>
using namespace std;
// Function to find starting and end index
void findIndex(int a[], int n, int key)
{
int start = -1;
// Traverse from beginning to find
// first occurrence
for (int i = 0; i < n; i++) {
if (a[i] == key) {
start = i;
break;
}
}
if (start == -1) {
cout << "Key not present in array";
return;
}
// Traverse from end to find last
// occurrence.
int end = start;
for (int i = n - 1; i >= start; i--) {
if (a[i] == key) {
end = i;
break;
}
}
if (start == end)
cout << "Only one key is present at index : "
<< start;
else {
cout << "Start index: " << start;
cout << "nLast index: " << end;
}
}
// Driver Code
int main()
{
int a[] = { 1, 2, 7, 8, 8, 9, 8, 0, 0, 0, 8 };
int n = sizeof(a) / sizeof(a[0]);
// Key to find
int key = 8;
// Calling function
findIndex(a, n, key);
return 0;
}
Java 语言(一种计算机语言，尤用于创建网站)
// Java program to find starting and ending
// indexes of repeated numbers in an array
class Test {
// Function to find starting and end index
static void findIndex(int a[], int n, int key)
{
int start = -1;
// Traverse from beginning to find
// first occurrence
for (int i = 0; i < n; i++) {
if (a[i] == key) {
start = i;
break;
}
}
if (start == -1) {
System.out.println("Key not present in array");
return;
}
// Traverse from end to find last
// occurrence.
int end = start;
for (int i = n - 1; i >= start; i--) {
if (a[i] == key) {
end = i;
break;
}
}
if (start == end)
System.out.println("Only one key is present at index : " + start);
else {
System.out.println("Start index: " + start);
System.out.println("Last index: " + end);
}
}
// Driver method
public static void main(String args[])
{
int a[] = { 1, 2, 7, 8, 8, 9, 8, 0, 0, 0, 8 };
// Key to find
int key = 8;
// Calling method
findIndex(a, a.length, key);
}
}
Python 3
# Python3 code to find starting and ending
# indexes of repeated numbers in an array
# Function to find starting and end index
def findIndex (a, n, key ):
start = -1
# Traverse from beginning to find
# first occurrence
for i in range(n):
if a[i] == key:
start = i
break
if start == -1:
print("Key not present in array")
return 0
# Traverse from end to find last
# occurrence.
end = start
for i in range(n-1, start - 1, -1):
if a[i] == key:
end = i
break
if start == end:
print("Only one key is present at index : ", start)
else:
print("Start index: ", start)
print("Last index: ", end)
# Driver Code
a = [1, 2, 7, 8, 8, 9, 8, 0, 0, 0, 8]
n = len(a)
# Key to find
key = 8
# Calling function
findIndex(a, n, key)
# This code is contributed by "Sharad_Bhardwaj".
C
// C# program to find starting and ending
// indexes of repeated numbers in an array
using System;
class GFG {
// Function to find starting and
// end index
static void findIndex(int[] a, int n,
int key)
{
int start = -1;
// Traverse from beginning to
// find first occurrence
for (int i = 0; i < n; i++) {
if (a[i] == key) {
start = i;
break;
}
}
if (start == -1) {
Console.WriteLine("Key not "
+ "present in array");
return;
}
// Traverse from end to find last
// occurrence.
int end = start;
for (int i = n - 1; i >= start; i--) {
if (a[i] == key) {
end = i;
break;
}
}
if (start == end)
Console.WriteLine("Only one key is"
+ " present at index : "
+ start);
else {
Console.WriteLine("Start index: "
+ start);
Console.WriteLine("Last index: "
+ end);
}
}
// Driver method
public static void Main()
{
int[] a = { 1, 2, 7, 8, 8, 9,
8, 0, 0, 0, 8 };
// Key to find
int key = 8;
// Calling method
findIndex(a, a.Length, key);
}
}
// This code is contributed by parashar.
服务器端编程语言（Professional Hypertext Preprocessor 的缩写）
<?php
// PHP program to find starting and ending
// indexes of repeated numbers in an array
// Function to find starting and end index
function findIndex($arr, $find){
// To store the atrting and
// the ending index of the key
$start = -1;
$end = -1;
// For every element of the given array
foreach ($arr as $key => $value) {
// If current element is equal
// to the given key
if($find === $value){
// If starting index hasn't been set
if($start==-1)
$start = $key;
$end = $key;
}
}
// If key is not present in the array
if($start==-1){
return "Key not present in array";
}
if($end == $start){
return "Only one key is present "." at index : ". $start;
}
return "Start index: ".$start. "\nLast index: ".$end;
}
// Driver code
$a = array(1, 2, 7, 8, 8, 9, 8, 0, 0, 0, 8);
// Key to find
$key = 8;
// Calling function
echo findIndex($a, $key);
?>
java 描述语言
<script>
// Javascript program to find starting and ending
// indexes of repeated numbers in an array
// Function to find starting and end index
function findIndex(a, n, key)
{
let start = -1;
// Traverse from beginning to find
// first occurrence
for (let i = 0; i < n; i++) {
if (a[i] == key) {
start = i;
break;
}
}
if (start == -1) {
document.write("Key not present in array");
return;
}
// Traverse from end to find last
// occurrence.
let end = start;
for (let i = n - 1; i >= start; i--) {
if (a[i] == key) {
end = i;
break;
}
}
if (start == end)
document.write("Only one key is present at index : "
+ start);
else {
document.write("Start index: " + start);
document.write("<br>" + "Last index: " + end);
}
}
// Driver Code
let a = [ 1, 2, 7, 8, 8, 9, 8, 0, 0, 0, 8 ];
let n = a.length;
// Key to find
let key = 8;
// Calling function
findIndex(a, n, key);
//This code is contributed by Mayank Tyagi
</script>
输出:
Start index: 3
Last index: 10
相关文章: 查找排序数组中某个元素的第一次和最后一次出现 本文由 Sahil Rajput 供稿。如果你喜欢 GeeksforGeeks 并想投稿，你也可以使用write.geeksforgeeks.org写一篇文章或者把你的文章邮寄到 contribute@geeksforgeeks.org。看到你的文章出现在极客博客主页上，帮助其他极客。 如果发现有不正确的地方，或者想分享更多关于上述话题的信息，请写评论。
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