How to find the position of a number in an array?
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Arnab Pal
il 15 Feb 2018
Commentato: Walter Roberson
il 20 Lug 2022
If I have a vector, a = [7 8 8 2 5 6], how do I compute the positions of the value 8?
I expect 2 and 3 or (1,2) and (1,3).
0 Commenti
Risposta accettata
Walter Roberson
il 15 Feb 2018
Modificato: MathWorks Support Team
il 27 Feb 2020
You can use the “find” function to return the positions corresponding to an array element value. For example:
a = [7 8 8 2 5 6];
linearIndices = find(a==8)
linearIndices =
2 3
To get the row and column indices separately, use:
[row,col] = find(a==8)
row =
1 1
col =
2 3
If you only need the position of one occurrence, you could use the syntax “find(a==8,1)”. You can also specify a direction if you specifically want the first or last occurrence, such as “find(a==8,1,’first’). For more information on these options, see “find”.
2 Commenti
Walter Roberson
il 20 Lug 2022
find() can never return 0. Perhaps you are looking at ans for a different operation?
Più risposte (4)
Bhagyesh Shiyani
il 5 Dic 2019
what if i want both 8 positions, any code?
2 Commenti
Walter Roberson
il 15 Gen 2020
This will not return value and index, it will return row and column numbers.
Sorne Duong
il 21 Lug 2021
a = 1, 3, 6, 9, 10, 15
We know the fourth value is 9, but how to find the fourth value in MATLAB?
4 Commenti
Nilesh Kumar Bibhuti
il 15 Ott 2021
Modificato: Walter Roberson
il 15 Ott 2021
BRO , THIS WILL GIVE U THE DESIRED OUTPUT . HAPPY CODING :)
#include <stdio.h>
#define MAX_SIZE 100 // Maximum array size
int main()
{
int arr[MAX_SIZE] ,brr[MAX_SIZE] ;
int size, i, toSearch, found ,k=0;
/* Input size of array */
printf("Enter size of array: ");
scanf("%d", &size);
/* Input elements of array */
printf("Enter elements in array: ");
for (i = 0; i < size; i++)
{
scanf("%d", &arr[i]);
}
printf("\nEnter element to search: ");
scanf("%d", &toSearch);
for (i = 0; i < size; i++)
{
if (arr[i] == toSearch)
{
brr[k] = i+1 ;
printf("%d ",brr[k]);
k++ ;
}
}
return 0;
}
1 Commento
Walter Roberson
il 15 Ott 2021
In C, int size should really be size_t size and your scanf() should be using %lu instead of %d . i and k should also be size_t
You should be checking the return status of each scanf() call .
Also
int main()
should be
int main(void)
unless you are using K&R C from before C was standardized.
The user is expecting the positions to be returned, rather than displayed.
You probably shouldn't be assuming integer for the array, but that would be an acceptable limitation if specifically documented.
You do not use or initialize found.
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