Test If a Vector Contains a Given Element

check if a std::vector contains a certain object?

Checking if v contains the element x:

#include <algorithm>

if(std::find(v.begin(), v.end(), x) != v.end()) {
    /* v contains x */
} else {
    /* v does not contain x */
}

Checking if v contains elements (is non-empty):

if(!v.empty()){
    /* v is non-empty */
} else {
    /* v is empty */
}

Test if a vector contains a given element

Both the match() (returns the first appearance) and %in% (returns a Boolean) functions are designed for this.

v <- c('a','b','c','e')

'b' %in% v
## returns TRUE

match('b',v)
## returns the first location of 'b', in this case: 2

Check if a vector contains object with already entered values

first of all, you can check count of std::vector to see if given key exists

//std::count(v.begin(), v.end(), key)
if (std::count(v.begin(), v.end(), key)){
    //it is inside
}
else{
    //it isn't inside
}

This is one way to go, but you should do the map

std::map<std::string,int> myMap;
//adding will look like this
std::pair<std::string,int> element;
myMap.insert(element);
//or
myMap.insert(std::pair<std::string,int>(myString,myInt));

Will solve your problem. You add pair of string and int.
In order to check if given key exists you can do

std::map<std::string, int> m;
if ( m.find(key) == m.end() ) {
  // not found
} else {
  // found
}

Added Kyle comment to, as it is valid way, and it looks a bit cleaner, you can also find if element exists like this

if (m.count(key)){
    //key found
}
else{
    //key not found
}

PS. It's bad practice to use c++ using namespace std;. You should always use std::whatever_you_need instead

How to find out if an item is present in a std::vector?

You can use std::find from <algorithm>:

#include <algorithm>
#include <vector>
vector<int> vec; 
//can have other data types instead of int but must same datatype as item 
std::find(vec.begin(), vec.end(), item) != vec.end()

This returns an iterator to the first element found. If not present, it returns an iterator to one-past-the-end. With your example:

#include <algorithm>
#include <vector>

if ( std::find(vec.begin(), vec.end(), item) != vec.end() )
   do_this();
else
   do_that();

R - test if a string vector contains any element of another list

You can get this using grepl.

lst_A <- c("TET","RNR")
lst_B = c("RNR_B","BC_TET")

Pattern = paste(lst_A, collapse="|")
grepl(Pattern, lst_B)

library(data.table)
DT_result <- data.table(lst_B, result=grepl(Pattern, lst_B))
DT_result
    lst_B result
1:  RNR_B   TRUE
2: BC_TET   TRUE

Addition

To respond to a comment, here is an example with more strings to test. Some pass the test, others not.

lst_A <- c("TET","RNR")
lst_B = c("RNR_B","BC_TET", "Fred", "RNR_A", "Zero", "ABC_TET")

Pattern = paste(lst_A, collapse="|")

DT_result <- data.table(lst_B, result=grepl(Pattern, lst_B))
DT_result
     lst_B result
1:   RNR_B   TRUE
2:  BC_TET   TRUE
3:    Fred  FALSE
4:   RNR_A   TRUE
5:    Zero  FALSE
6: ABC_TET   TRUE

How can I determine whether a vector contains another vector respecting order in R?

You can collapse your vector into a regex pattern and use grepl

vec1 <- c("a", "b", "c")
vec2 <- c("a", "b", "c", "d", "e")
grepl(paste(vec1, collapse=".*"), paste(vec2, collapse=""))
# TRUE
vec3 <- c("e", "d", "c", "b", "a")
grepl(paste(vec1, collapse=".*"), paste(vec3, collapse=""))
# FALSE
vec4 <- c("a", "x", "b", "c", "y")
grepl(paste(vec1, collapse=".*"), paste(vec4, collapse=""))
# TRUE

EDIT: Based on G5W's comment, you can add a delimiter in case each element is not a character but might be a short string. The delimiter will break up the entries of your vector

vec5 <- c("a", "b", "c")
vec6 <- c("ab", "c")
vec7 <- c("ab", "e", "c", "d")
grepl(paste(vec5, collapse="-.*"), paste(vec7, collapse="-"))
# FALSE
grepl(paste(vec6, collapse="-.*"), paste(vec7, collapse="-"))
# TRUE

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