CS50x threads to aide as a supplementary resource › Forums › CS50’s Introduction to Computer Science by Harvard University on Edx › Week 3: [Algorithms] – Linear Search, Binary Search, Bubble Sort, Selection Sort, Recursion, Merge Sort › find_min function and infinite loop when a candidate not winner in first instance
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January 17, 2023 at 4:25 am #1043
// Return the minimum number of votes any remaining candidate has int find_min(void) { int mini; for (int cc = 0; cc < candidate_count; cc++) { if (candidates[cc].votes < candidates[cc + 1].votes) { mini = candidates[cc].votes; } } return mini; return 0; }
There must be something wrong with the above code. Not sure if line no. 12 and line no. 13 are okay. My understanding is if mini gets no integer value (tie case), return mini will be bypassed by return 0. Thought to put return mini within for loop on line no. 11 but that will not be the final mini value obtained by checking all the vote counts of candidates.
Here is the state of code currently. While the code apparently works correctly when the winning candidate is decided on first instance, there is an infinite loop if that not be the case.
#include <cs50.h> #include <stdio.h> #include <string.h> #include <stdlib.h> // Max voters and candidates #define MAX_VOTERS 100 #define MAX_CANDIDATES 9 // preferences[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.name = argv; candidates.votes = 0; candidates.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("%i, %i, %s\n", i + 1, j + 1, candidates[preferences[j]].name); } } //printf("complete"); // 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.eliminated) { printf("%s\n", candidates.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.votes = 0; } } return 0; } // Record preference if vote is valid bool vote(int voter, int rank, string name) { //printf("voter no (via local function taking value of voter as argument).: %i, rank selected (via local function taking value of rank as argument) %i\n", voter + 1, rank + 1); for (int t = 0; t < candidate_count; t++) { if(strcmp(name, candidates[t].name) == 0) { preferences[voter][rank] = t; //printf("preference of voter no. %i for rank %i is %s\n", voter + 1, rank + 1, candidates[t].name); return 4; } } return 0; } // Tabulate votes for non-eliminated candidates void tabulate(void) { int vc = 0; int cc = 0; for (vc = 0; vc < voter_count; vc++) { for (cc = 0; cc < candidate_count; cc++) { if (candidates[preferences[vc][cc]].eliminated != 1) { int t = preferences[vc][cc]; candidates[t].votes = candidates[t].votes + 1; printf("vote secured by %s for rank 1 is %i", candidates[t].name, candidates[t].votes); break; } } } return; } // Print the winner of the election, if there is one bool print_winner(void) { int necand = 0; for (int cc = 0; cc < candidate_count; cc++) { if (candidates[cc].eliminated == false) { necand = necand + 1; } } for (int canc = 0; canc < candidate_count; canc++) { if (candidates[canc].votes > necand/2) { printf("winner is %s", candidates[canc].name); return true; break; } } return false; } // Return the minimum number of votes any remaining candidate has int find_min(void) { int mini; for (int cc = 0; cc < candidate_count; cc++) { if (candidates[cc].votes < candidates[cc + 1].votes) { mini = candidates[cc].votes; } } return mini; return 0; } // Return true if the election is tied between all candidates, false otherwise bool is_tie(int min) { int tievalue; for (int cc = 0; cc < candidate_count; cc++) { tievalue = candidates[cc].votes; if (candidates[cc].votes != tievalue) { return 1; } } return false; } // Eliminate the candidate (or candidates) in last place void eliminate(int min) { for (int cc = 0; cc < candidate_count; cc++) { if (candidates[cc].votes == min) { candidates[cc].eliminated = 1; } } return; }
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https://edstem.org/us/courses/176/discussion/2392767?comment=5463010[learn_press_profile]
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