目标是模仿排名选择投票系统，其中选民将为所有候选人投票，并根据他们的偏好对其进行排名。要想赢得候选人，他必须拥有超过50％的选票。
输出：
./runoff Alice Bob Charlie Number of voters: 5 Rank 1: Alice Rank 2: Charlie Rank 3: Bob Rank 1: Alice Rank 2: Charlie Rank 3: Bob Rank 1: Bob Rank 2: Charlie Rank 3: Alice Rank 1: Bob Rank 2: Charlie Rank 3: Alice Rank 1: Charlie Rank 2: Alice Rank 3: Bob Alice在这种情况下，爱丽丝获胜是因为爱丽丝和鲍勃并列获胜，但是由于最后一名选民更喜欢查理，因为查理获得了最少的选票，因此查理被淘汰出局。而且由于该选民比鲍勃更喜欢爱丽丝，所以爱丽丝获得了投票，所以爱丽丝赢得了比赛。
我的代码：
#include <cs50.h>
#include <stdio.h>
#include <string.h>
// Max voters and candidates
#define MAX_VOTERS 100
#define MAX_CANDIDATES 9
// preferences[i][j] is jth preference for voter i
int preferences[MAX_VOTERS][MAX_CANDIDATES];
// Candidates have name, vote count, eliminated status
typedef struct
{
string name;
int votes;
bool eliminated;
}
candidate;
// Array of candidates
candidate candidates[MAX_CANDIDATES];
// Numbers of voters and candidates
int voter_count;
int candidate_count;
// Function prototypes
bool vote(int voter, int rank, string name);
void tabulate(void);
bool print_winner(void);
int find_min(void);
bool is_tie(int min);
void eliminate(int min);
int main(int argc, string argv[])
{
// Check for invalid usage
if (argc < 2)
{
printf("Usage: runoff [candidate ...]\n");
return 1;
}
// Populate array of candidates
candidate_count = argc - 1;
if (candidate_count > MAX_CANDIDATES)
{
printf("Maximum number of candidates is %i\n", MAX_CANDIDATES);
return 2;
}
for (int i = 0; i < candidate_count; i++)
{
candidates[i].name = argv[i + 1];
candidates[i].votes = 0;
candidates[i].eliminated = false;
}
voter_count = get_int("Number of voters: ");
if (voter_count > MAX_VOTERS)
{
printf("Maximum number of voters is %i\n", MAX_VOTERS);
return 3;
}
// Keep querying for votes
for (int i = 0; i < voter_count; i++)
{
// Query for each rank
for (int j = 0; j < candidate_count; j++)
{
string name = get_string("Rank %i: ", j + 1);
// Record vote, unless it's invalid
if (!vote(i, j, name))
{
printf("Invalid vote.\n");
return 4;
}
}
printf("\n");
}
// Keep holding runoffs until winner exists
while (true)
{
// Calculate votes given remaining candidates
tabulate();
// Check if election has been won
bool won = print_winner();
if (won)
{
break;
}
// Eliminate last-place candidates
int min = find_min();
bool tie = is_tie(min);
// If tie, everyone wins
if (tie)
{
for (int i = 0; i < candidate_count; i++)
{
if (!candidates[i].eliminated)
{
printf("%s\n", candidates[i].name);
}
}
break;
}
// Eliminate anyone with minimum number of votes
eliminate(min);
// Reset vote counts back to zero
for (int i = 0; i < candidate_count; i++)
{
candidates[i].votes = 0;
}
}
return 0;
}
// Record preference if vote is valid
bool vote(int voter, int rank, string name)
{
// TODO
for (int i = 0; i < candidate_count; i++)
{
if (strcmp(name, candidates[i].name) == 0)
{
preferences[voter][rank] = i;
return true;
}
}
return false;
}
// Tabulate votes for non-eliminated candidates
void tabulate(void)
{
for (int i = 0; i < voter_count; i++)
{
for (int j = 0; j < candidate_count; j++)
{
if (!candidates[preferences[i][j]].eliminated)
{
candidates[preferences[i][j]].votes++;
break;
}
}
}
return;
}
// Print the winner of the election, if there is one
bool print_winner(void)
{
for (int i = 0; i < candidate_count; i++)
{
if (candidates[i].votes > (candidate_count * 0.5))
{
printf("%s\n", candidates[i].name);
return true;
}
}
return false;
}
// Return the minimum number of votes any remaining candidate has
int find_min(void)
{
int min = 0;
for (int i = 0; i < candidate_count; i++)
{
if (!candidates[i].eliminated)
{
if (candidates[i].votes > min)
min = candidates[i].votes;
}
}
return min;
}
// Return true if the election is tied between all candidates, false otherwise
bool is_tie(int min)
{
for (int i = 0; i < candidate_count; i++)
{
if (candidates[i].votes != min && !candidates[i].eliminated)
return false;
}
return true;
}
// Eliminate the candidate (or candidiates) in last place
void eliminate(int min)
{
for (int i = 0; i < candidate_count; i++)
{
if (candidates[i].votes == min)
candidates[i].eliminated = true;
}
return;
}
我收到这些错误...
:) runoff.c exists
:) runoff compiles
:) vote returns true when given name of candidate
:) vote returns false when given name of invalid candidate
:) vote correctly sets first preference for first voter
:) vote correctly sets third preference for second voter
:) vote correctly sets all preferences for voter
:) tabulate counts votes when all candidates remain in election
:) tabulate counts votes when one candidate is eliminated
:) tabulate counts votes when multiple candidates are eliminated
:( print_winner prints name when someone has a majority
print_winner did not print winner of election
:( print_winner returns true when someone has a majority
print_winner did not print winner and then return true
:( print_winner returns false when nobody has a majority
print_winner did not return false
:( print_winner returns false when leader has exactly 50% of vote
print_winner did not return false
:) find_min returns minimum number of votes for candidate
:) find_min returns minimum when all candidates are tied
:) find_min ignores eliminated candidates
:) is_tie returns true when election is tied
:) is_tie returns false when election is not tied
:) is_tie returns false when only some of the candidates are tied
:) is_tie detects tie after some candidates have been eliminated
:) eliminate eliminates candidate in last place
:) eliminate eliminates multiple candidates in tie for last
:) eliminate eliminates candidates after some already eliminated
答案 0 :(得分：0)
好吧，我明白了... foreach($array as $k => $a) {
array_pop($array[$k]);
}
候选人编号错误，应该是if (candidates[i].votes > (candidate_count * 0.5))