C - 为什么这个循环会经历两次？

Question

这个函数假设在连接4游戏中返回1步,但是,它返回两次...我用调试器完成了这个功能,它似乎跳过了getc()调用我不知道为什么.任何帮助深表感谢!

char UndoBoard(char x[ROWS][COLS], char * player){
    struct Node* temp = head;
    int i,j;
    temp = temp->next;
    char input = 'q';
    while((input != 'q' || input != 'Q') && temp != NULL){
        for (i=0;i<ROWS;i++){
            for (j=0;j<COLS;j++){
            x[i][j] = temp->data[i][j];
            }
        }
        printBoard(x);
        if(*player == 'O')*player = 'X';
        else *player = 'O';
        printf("b - undo one step more, f - go forward, q - resume game from here\n");
        input = getc(stdin);
        if(input == 'q' || input == 'Q')break;
        temp = temp -> next;
    }
}

Answer 1

用于的逻辑

while((input != 'q' || input != 'Q') && temp != NULL){

是有缺陷的.你需要使用:

while((input != 'q' && input != 'Q') && temp != NULL){