如何计算结构中的字符字符串？

Question

Is there a way to count how many times a name appears in the struct?

This is basically what i am trying to make: Create a program that will determine the number of times a name occurs in a list.

The user will enter a name that appears then the output is the number on how many times the name entered appear in the list.

#include<stdio.h>

typedef struct Person {
    char name[50];
} Person;

void print_people(const Person *people) {
    for (size_t i = 0; people[i].name[0]; ++i)
        printf("%-20s \n", people[i].name);
}

int main() {

    Person people[] = { {"Alan"}, {"Bob"}, {"Alan"}, {"Carol"}, {"Bob"}, {"Alan"} };
    print_people(people);
    char name;

    return 0;

}

Answer 1

First of all, your function print_people has a bug. The line

for (size_t i = 0; people[i].name[0]; ++i)

is wrong. It will read from the array out of bounds, because the loop condition people[i].name[0] is wrong. This loop condition would only be correct if the array were terminated by an element which has name[0] set to '\0' . This was the case in the original version of your question, but not in your current version.

Therefore, you should change the line to the following:

for (size_t i = 0; i < 6; ++i)

In order to count the number of people with a certain name, all you have to do is traverse the array in the same way as you are doing it in the function print_people and count the number of times you encounter the name you are searching for:

int count_person( const Person *people, const char *target ) {

    int count = 0;

    for ( int i = 0; i < 6; i++ )
        if ( strcmp( people[i].name, target ) == 0 )
            count++;

    return count;
}

Your entire program would then look like this:

#include <stdio.h>
#include <string.h>

typedef struct Person {
    char name[50];
} Person;

void print_people(const Person *people) {
    for (size_t i = 0; i < 6; ++i)
        printf("%-20s \n", people[i].name);
}

int count_person( const Person *people, const char *target ) {

    int count = 0;

    for ( int i = 0; i < 6; i++ )
        if ( strcmp( people[i].name, target ) == 0 )
            count++;

    return count;
}

int main() {

    Person people[] = { {"Alan"}, {"Bob"}, {"Alan"}, {"Carol"}, {"Bob"}, {"Alan"} };

    printf( "Number of occurances of \"Alan\": %d\n", count_person( people, "Alan" ) );

    return 0;
}

This program has the following output:

Number of occurances of "Alan": 3

Answer 2

You might want a function like this:

int count_person(const Person *people,const Person who) {
    int whocount = 0;

    for (size_t i = 0; people[i].name[0]; ++i)
        if (strcmp(people[i].name,who.name) == 0)
            whocount++;
    return whocount;
}