Do循環生成唯一的隨機排列

Question

的陣列我已經寫了一些代碼來生成結構的數組。 id變量旨在是唯一的並隨機生成。然而，似乎是發生的是，如果生成函數（其中gnerates和填充結構的數組）數組中遇到的匹配數量，標誌變量設置爲0，並退出do循環不創建一個新的隨機數重新檢查一場比賽。然後，當循環退出時，代碼繼續，並將匹配的隨機數分配給數組中的空白點。作爲一個警告，我意識到這將是簡單的只是把所有10個可能的整數，移動他們，並填補了數組，但我想用一個小樣本，所以我可以看它的獲得）蘭特的竅門（在調試器中執行。我懷疑我只是盯着這太久，嘗試了太多的東西，但任何建議，將不勝感激。謝謝。

編輯：只是爲了澄清我的問題特別是涉及到做循環，我需要做的，以確保當找到匹配，程序將生成一個新的隨機號碼，並開始再次匹配搜索的內容。這應該爲數組中的每個位置重複，直到每個id元素都是唯一的。目前，當我運行該程序時，我仍然得到重複的數字。

#include <stdio.h> 
#include<stdlib.h> 
#include<math.h> 
#include<conio.h> 
#include<assert.h> 

struct student{ 
    int id; 
    int score; 
}; 

struct student* allocate(){ 
    /*Allocate memory for ten students*/ 
    struct student* s = malloc(10 * sizeof(struct student)); 
    assert (s != 0); 

    /*return the pointer*/ 
    return s; 
} 

void generate(struct student* students){ 
    /*Generate random ID and scores for ten students, ID being between 1 and 10, scores between 0 and 100*/ 
    int i, j; 
    int flag; 
    int randNum = 0; 
    for (i = 0; i < 10; i++) { 
     flag = 1; 
     do { 
      randNum = (rand()%10 + 1); //generate random ID for each student 

      for (j = 0; j < 10 && flag == 1; j++) { //search array for matching numbers 
       if (students[j].id == randNum) { 
        flag = 0; 
       } 
       if (j == 9 && flag == 1) { 
        flag = 0; 
       } 
      } 
     } 
     while (flag == 1); //set condition 

     students[i].id = randNum; 
     students[i].score = (rand()%(100 - 0 + 1) + 0); //generate random score for each student 
    } 
} 


void output(struct student* students){ 
    /*Output information about the ten students in the format: 
       ID1 Score1 
       ID2 score2 
       ID3 score3 
       ... 
       ID10 score10*/ 
     int i; 
     printf("Student scores: \n\n"); 
     for (i = 0; i < 10; i++) { 
      printf("\t%d, %d\n", students[i].id, students[i].score); 
     } 
} 

void summary(struct student* students){ 
    /*Compute and print the minimum, maximum and average scores of the ten students*/ 
    int sumS, minS, maxS, avgS, i, j, tempID, tempS; 
    printf("Sorted students by scores: \n"); 
    for (i = 0; i < 10; i++) { 
     sumS += students[i].score; 
     for (j = 0; j <10; j++) { 
      if (students[i].score < students[j].score) { 
       tempS = students[j].score; 
       tempID = students[j].id; 
       students[j].score = students[i].score; 
       students[j].id = students[i].id; 
       students[i].score = tempS; 
       students[i].id = tempID; 
      } 
     } 
    } 
    for (i = 0; i < 10; i++) { 
     printf("\t%d, %d\n", students[i].id, students[i].score); 
    } 
    printf("Minimum score: %d\n", minS = students[0].score); 
    printf("Maximum score: %d\n", maxS = students[9].score); 
    printf("Average score: %d", avgS = sumS/10); 
} 

void deallocate(struct student* stud){ 
    /*Deallocate memory from stud*/ 
    free(stud); 
} 

int main(){ 
    struct student* stud = NULL; 

    /*call allocate*/ 
    stud = allocate(); 

    /*call generate*/ 
    generate(stud); 

    /*call output*/ 
    output(stud); 

    /*call summary*/ 
    summary(stud); 

    /*call deallocate*/ 
    deallocate(stud); 

    return 0; 
} 

Answer 1

你的標誌設置爲0，如果已經選擇的號碼，所以你應該測試while(flag == 0)，並在循環的開始重新設置標記，以1：

do { 
    flag = 1; 
    randNum = (rand()%10 + 1); //generate random ID for each student 

    for (j = 0; j < i && flag == 1; j++) { //search array for matching numbers 
     if (students[j].id == randNum) { 
      flag = 0; 
     } 
    } 
} 
while (flag == 0); //set condition 

現在， flag == 0手段「已經看到了，再試一次」，並flag == 1意思是「這是一個新的號碼，繼續前進，它寫入陣列」。

此外，您只有指數< i填充的陣列插槽，所以比較循環不應該去9，但只能到i-1。