C语言中如何避免数组重复值？5×5棋盘rand()去重及排除0方案

Hey there! No worries at all—every programmer starts with these kinds of questions, so let's break this down step by step to fix your 5×5 board issue.

问题根源 #

Your current code has two key issues:

• rand() % 25 produces numbers from 0 to 24, which is why you're seeing 0 values.
• Since rand() generates pseudo-random numbers, there's a high chance of duplicates when calling it 25 times in a row.

最优解决方案：Fisher-Yates 洗牌算法 #

The best way to get a set of unique numbers from 1 to 25 is to first create a sorted list of these numbers, then shuffle them randomly. This guarantees no duplicates and no zeros. Here's how to implement it:

Step 1: Initialize a sorted array of 1-25 #

First, create a 1D array that holds all numbers from 1 to 25—this gives us our full set of non-repeating, non-zero values.

Step 2: Shuffle the array with Fisher-Yates #

This algorithm shuffles the array in-place, ensuring every permutation is equally likely, with no duplicates.

Step 3: Fill your 5×5 board from the shuffled array #

Once shuffled, we can iterate through the 1D array and map it to your 2D board.

Modified Code #

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

void createboard(int board[5][5]) { 
    int numbers[25];
    int i, temp, index;

    // Step 1: Fill numbers array with 1-25
    for (i = 0; i < 25; i++) {
        numbers[i] = i + 1;
    }

    // Step 2: Fisher-Yates shuffle
    for (i = 24; i > 0; i--) {
        // Generate a random index between 0 and i (inclusive)
        index = rand() % (i + 1);
        // Swap current element with the random index element
        temp = numbers[i];
        numbers[i] = numbers[index];
        numbers[index] = temp;
    }

    // Step 3: Fill the 5x5 board from the shuffled array
    int count = 0;
    for (int rows = 0; rows < 5; rows++) { 
        for (int columns = 0; columns < 5; columns++) { 
            board[rows][columns] = numbers[count];
            count++;
        } 
    }
}

int main() {
    // Important: Call srand() ONCE at the start of your program
    srand(time(NULL));

    int board[5][5];
    createboard(board);

    // Test: Print the board to verify
    for (int i = 0; i < 5; i++) {
        for (int j = 0; j < 5; j++) {
            printf("%3d", board[i][j]);
        }
        printf("\n");
    }

    return 0;
}

Key Notes #

• Call srand(time(NULL)) only once: Placing it in main() instead of createboard() prevents resetting the random seed multiple times (which can cause repeated sequences if the function is called quickly).
• Fisher-Yates is efficient: It runs in O(n) time, which is perfect for your 25-element array.
• No zeros, no duplicates: Since we start with 1-25 and just shuffle, you're guaranteed every number appears exactly once.

内容的提问来源于stack exchange，提问作者Quicky App