随机选择扬声器顺序的算法可以工作但通常会产生无限循环

>每位候选人被问到7个​​问题
>每个候选人在位置1,位置2等处恰好回答一次.
>候选人并不总是遵循相同的顺序(随机顺序但受限于前两个规则)

该算法有效,产生约束于规则的随机输出,但经常被无限循环(或出现).我已经无法确定为什么会发生这种情况,尽管逐步执行代码w /额外的日志记录/断点.

注意：此算法尚未推广或优化.

#include <stdio.h>
#include <time.h>
#include <stdlib.h>

#define NUM_ROWS 7
#define NUM_columNS 7

int debate_order[NUM_ROWS][NUM_columNS];
int candidate_used[NUM_ROWS];

void print_debate_order()
{
    int row,column;

    for(column = 0; column < NUM_columNS; column++) {
        printf("Questions #%d\n",column);
        for(row = 0; row < NUM_ROWS; row++)
            printf("  Candidate #%d\n",debate_order[column][row]);
    }
}

void set_unused(int *array,int sizE)
{
    int i;

    for(i = 0; i < size; i++)
        arraY[i] = -1;
}

int in_row(int candidate_num,int current_row)
{
    int column;
    for(column = 0; column < NUM_columNS; column++)
        if( debate_order[column][current_row] == -1 ) // reached end of columns filled in
            break;
        else if ( debate_order[column][current_row] == candidate_num ) // found the candidate in this row
            return(1);
    return(0);
}

int main(int argc,const char * argv[]) {
    int row,column;
    int rand_candidate;

    srand((unsigned int)time(NULL));
    for(column = 0; column < NUM_columNS; column++)
        set_unused(&debate_order[column][0],NUM_columNS);

    for(column = 0; column < NUM_columNS; column++) {
        set_unused(candidate_used,NUM_columNS);
        for (row = 0; row < NUM_ROWS; row++ ) {
            do {
                rand_candidate = rand() % 7;
            } while(candidate_used[rand_candidate] == 1 || in_row(rand_candidate,row));
            candidate_used[rand_candidate] = 1;
            debate_order[column][row] = rand_candidate;
        }
    }

    print_debate_order();

    return 0;
}