CS50 Plurality Problem, error: use of undeclared identifier 'i'

Question

正在尝试解决 CS50 的 pset3 复数问题 class，我的代码的第 93 行一直是问题所在，我在解决问题集的最后一部分时遇到了一些麻烦，即打印获胜者。

我认为投票总数部分没问题，但我无法获得获胜者部分的正确代码。当我 运行 代码时，我收到以下错误消息：

error: use of undeclared identifier 'i' printf("%s\n", candidates[i].name);

#include <cs50.h>
#include <stdio.h>
#include <string.h>

// Max number of candidates
#define MAX 9

// Candidates have name and vote count
typedef struct
{
    string name;
    int votes;
}
candidate;

// Array of candidates
candidate candidates[MAX];

// Number of candidates
int candidate_count;

// Function prototypes
bool vote(string name);
void print_winner(void);

int main(int argc, string argv[])
{
    // Check for invalid usage
    if (argc < 2)
    {
        printf("Usage: plurality [candidate ...]\n");
        return 1;
    }

    // Populate array of candidates
    candidate_count = argc - 1;

    if (candidate_count > MAX)
    {
        printf("Maximum number of candidates is %i\n", MAX);
        return 2;
    }
    for (int i = 0; i < candidate_count; i++)
    {
        candidates[i].name = argv[i + 1];
        candidates[i].votes = 0;
    }

    int voter_count = get_int("Number of voters: ");

    // Loop over all voters
    for (int i = 0; i < voter_count; i++)
    {
        string name = get_string("Vote: ");

        // Check for invalid vote
        if (!vote(name))
        {
            printf("Invalid vote.\n");
        }
    }

    // Display winner of election
    print_winner();
}

// Update vote totals given a new vote
bool vote(string name)
{
    for (int i = 0; i < candidate_count; i++)
    {
        if (strcmp(name, candidates[i].name) == 0)
            candidates[i].votes++;
    }

    return true; 
    return false;
}

// Print the winner (or winners) of the election
void print_winner(void)
{
    int maxvote = 0; 

    for (int i = 0; i <  candidate_count; i++)
    {
        if (candidates[i].votes > maxvote)
            maxvote = candidates[i].votes;
    }

    printf("%s\n", candidates[i].name);

    return;
}

Answer 1

i 变量仅在循环上下文中定义。当循环结束时，您的 print 语句尝试打印 candidates[i].name 但 i 不再定义。就像您保存最大票数一样，您还需要将候选索引保存在循环外声明的值中。

int maxvote = 0; 
int winnerIndex;

for (int i = 0; i <  candidate_count; i++)
{
    if (candidates[i].votes > maxvote) {
        maxvote = candidates[i].votes;
        winnerIndex = i;
    }
}
printf("%s\n", candidates[winnerIndex].name);