【C语言】学习笔记 第11章 指针 编程题 古城微笑少年丶 2024-03-22 10:46 11阅读 0赞 ### 【C语言】学习笔记 ### #### 文章目录 #### * * 【C语言】学习笔记 * * 第11章 指针 * * 编程题 #### 第11章 指针 #### ![在这里插入图片描述][0178fd20b6c04d3c92e9164a209e9079.png_pic_center] 指针是 C 语言最重要——也是最常被误解——的特性之一。 ##### 编程题 ##### 【1】修改第 2 章的编程题 7，使其包含下列函数： void pay_amount(int dollars, int *twenties, int *tens, int *fives, int *ones); 函数需要确定：为支付参数 dollars 表示的付款金额，所需 20 美元、10 美元、5 美元和 1 美元钞票 的最小数目。twenties 参数所指向的变量存储所需 20 美元钞票的数目，tens、fives 和 ones 参数 类似。 #include <stdio.h> void pay_amount(int dollars, int* twenties, int* tens, int* fives, int* ones); int main(void) { int amount; printf("Enter a dollar amount: "); scanf("%d", &amount); int twenty_note, ten_note, five_note, one_note; pay_amount(amount, &twenty_note, &ten_note, &five_note, &one_note); printf("$20 bills: %d\n", twenty_note); printf("$10 bills: %d\n", ten_note); printf("$5 bills: %d\n", five_note); printf("$1 bills: %d\n", one_note); return 0; } void pay_amount(int dollars, int* twenties, int* tens, int* fives, int* ones) { *twenties = dollars / 20; *tens = (dollars - *twenties * 20) / 10; *fives = (dollars - *twenties * 20 - *tens * 10) / 5; *ones = (dollars - *twenties * 20 - *tens * 10) % 5; } ![在这里插入图片描述][63d8ee0c6703432e86ded3c06bd8f1ad.png_pic_center] 【2】修改第 5 章的编程题 8，使其包含下列函数： void find_closest_flight(int desired_time, int *departure_time, int *arrival_time); 函数需查出起飞时间与 desired\_time（用从午夜开始的分钟数表示）最接近的航班。该航班的起飞 时间和抵达时间（也都用从午夜开始的分钟数表示）将分别存储在 departure\_time 和 arrival\_time 所指向的变量中。 #include<stdio.h> void find_closest_flight(int desired_time, int* departure_time, int* arrival_time); int main(void) { int departure, arrive; int hour, minute; int input_minutes; printf("Enter a 24-hour time: "); scanf("%d:%d", &hour, &minute); input_minutes = hour * 60 + minute; find_closest_flight(input_minutes, &departure, &arrive); printf("%d", departure); return 0; } void find_closest_flight(int desired_time, int* departure_time, int* arrival_time) { if (desired_time < (615) / 2) { *departure_time = 21 * 60 + 45; *arrival_time = 24 * 60 - 2; } else if (desired_time < (8 * 60 + 9 * 60 + 43) / 2) { *departure_time = 8 * 60; *arrival_time = 10 * 60 + 16; } else if (desired_time < (9 * 60 + 43 + 11 * 60 + 19) / 2) { *departure_time = 9 * 60 + 43; *arrival_time = 11 * 60 + 52; } else if (desired_time < (11 * 60 + 19 + 12 * 60 + 47) / 2) { *departure_time = 11 * 60 + 19; *arrival_time = 13 * 60 + 31; } else if (desired_time < (12 * 60 + 47 + 14 * 60) / 2) { *departure_time = 12 * 60 + 47; *arrival_time = 15 * 60; } else if (desired_time < (14 * 60 + 15 * 60 + 45) / 2) { *departure_time = 14 * 60; *arrival_time = 16 * 60 + 8; } else if (desired_time < (15 * 60 + 45 + 19 * 60) / 2) { *departure_time = 15 * 60 + 45; *arrival_time = 17 * 60 + 55; } else if (desired_time < (15 * 60 + 21 * 60 + 45) / 2) { *departure_time = 19 * 60; *arrival_time = 21 * 60 + 20; } else { *departure_time = 21 * 60 + 45; *arrival_time = 24 * 60 - 2; } } ![在这里插入图片描述][779963d479334c2ba3ca86e9a20604ae.png_pic_center] 【3】修改第 6 章的编程题 3，使其包含下列函数： void reduce(int numerator, int denominator, int *reduced_numerator, int *reduced_denominator); numerator 和 denominator 分别是分数的分子和分母。reduced\_numerator 和 reduced\_denominator 是指向变量的指针，相应变量中分别存储把分数化为最简形式后的分子和分母。 #include<stdio.h> void reduce(int numerator, int denominator, int* reduced_numerator, int* reduced_denominator); int main(void) { int top, bottom; printf("Enter a fraction: "); scanf("%d/%d", &top, &bottom); reduce(top, bottom, &top, &bottom); printf("In lowest terms: %d/%d", top, bottom); return 0; } void reduce(int numerator, int denominator, int* reduced_numerator, int* reduced_denominator) { int remainder; while (denominator != 0) { remainder = numerator % denominator; numerator = denominator; denominator = remainder; } *reduced_numerator /= numerator; *reduced_denominator /= numerator; } ![在这里插入图片描述][715f6bf2a99046d594c2964621a3e156.png_pic_center] 【4】修改 10.5 节的 poker.c 程序，把所有的外部变量移到 main 函数中，并修改各个函数，使它们通过参 数进行通信。analyze\_hand函数需要修改变量 straight、flush、four、three和 pairs，所以它需要以指向这些变量的指针作为参数。 /* Classifies a poker hand */ #include <stdbool.h> #include <stdio.h> #include <stdlib.h> #define NUM_RANKS 13 #define NUM_SUITS 4 #define NUM_CARDS 5 void read_cards(int num_in_rank[], int num_in_suit[]); void analyze_hand(int num_in_rank[], int num_in_suit[], bool* straight, bool* flush, bool* four, bool* three, int* pairs); void print_result(bool straight, bool flush, bool four, bool three, int pairs); /************************************************************ * main: Calls read_cards, analyze_hand, and print_result * * repeatedly. * ************************************************************/ int main(void) { int num_in_rank[NUM_RANKS]; int num_in_suit[NUM_SUITS]; bool straight, flush, four, three; int pairs; /* can be 0, 1, or 2 */ read_cards(num_in_rank, num_in_suit); analyze_hand(num_in_rank, num_in_suit, &straight, &flush, &four, &three, &pairs); print_result(straight, flush, four, three, pairs); return 0; } /************************************************************ * read_cards: Reads the cards into the external * * variables num_in_rank and num_in_suit; * * checks for bad cards and duplicate cards. * ************************************************************/ void read_cards(int num_in_rank[], int num_in_suit[]) { bool card_exists[NUM_RANKS][NUM_SUITS]; char ch, rank_ch, suit_ch; int rank, suit; bool bad_card; int cards_read = 0; for (rank = 0; rank < NUM_RANKS; rank++) { num_in_rank[rank] = 0; for (suit = 0; suit < NUM_SUITS; suit++) card_exists[rank][suit] = false; } for (suit = 0; suit < NUM_SUITS; suit++) num_in_suit[suit] = 0; while (cards_read < NUM_CARDS) { bad_card = false; printf("Enter a card: "); rank_ch = getchar(); switch (rank_ch) { case '0': exit(EXIT_SUCCESS); case '2': rank = 0; break; case '3': rank = 1; break; case '4': rank = 2; break; case '5': rank = 3; break; case '6': rank = 4; break; case '7': rank = 5; break; case '8': rank = 6; break; case '9': rank = 7; break; case 't': case 'T': rank = 8; break; case 'j': case 'J': rank = 9; break; case 'q': case 'Q': rank = 10; break; case 'k': case 'K': rank = 11; break; case 'a': case 'A': rank = 12; break; default: bad_card = true; } suit_ch = getchar(); switch (suit_ch) { case 'c': case 'C': suit = 0; break; case 'd': case 'D': suit = 1; break; case 'h': case 'H': suit = 2; break; case 's': case 'S': suit = 3; break; default: bad_card = true; } while ((ch = getchar()) != '\n') if (ch != ' ') bad_card = true; if (bad_card) printf("Bad card; ignored.\n"); else if (card_exists[rank][suit])printf("Duplicate card; ignored.\n"); else { num_in_rank[rank]++; num_in_suit[suit]++; card_exists[rank][suit] = true; cards_read++; } } } /************************************************************ * analyze_hand: Determines whether the hand contains a * * straight, a flush, four-of-a-kind, * * and/or three-of-a-kind; determines the * * number of pairs; stores the results into * * the external variables straight, flush, * * four, three, and pairs. * ************************************************************/ void analyze_hand(int num_in_rank[], int num_in_suit[], bool* straight, bool* flush, bool* four, bool* three, int* pairs) { int num_consec = 0; int rank, suit; *straight = false; *flush = false; *four = false; *three = false; *pairs = 0; /* check for flush */ for (suit = 0; suit < NUM_SUITS; suit++) if (num_in_suit[suit] == NUM_CARDS) *flush = true; /* check for straight */ rank = 0; while (num_in_rank[rank] == 0) rank++; for (; rank < NUM_RANKS && num_in_rank[rank] > 0; rank++) num_consec++; if (num_consec == NUM_CARDS) { *straight = true; return; } /* check for 4-of-a-kind, 3-of-a-kind, and pairs */ for (rank = 0; rank < NUM_RANKS; rank++) { if (num_in_rank[rank] == 4) *four = true; if (num_in_rank[rank] == 3) *three = true; if (num_in_rank[rank] == 2) *pairs++; } } /************************************************************ * print_result: prints the classification of the hand, * * based on the values of the external * * variables straight, flush, four, three, * * and pairs. * ************************************************************/ void print_result(bool straight, bool flush, bool four, bool three, int pairs) { if (straight && flush) printf("Straight flush"); else if (four) printf("Four of a kind"); else if (three && pairs == 1) printf("Full house"); else if (flush) printf("Flush"); else if (straight) printf("Straight"); else if (three) printf("Three of a kind"); else if (pairs == 2) printf("Two pairs"); else if (pairs == 1) printf("Pair"); else printf("High card"); printf("\n\n"); } ![在这里插入图片描述][b9bd5b896f714a54b1bbe637d0f18127.png_pic_center] [0178fd20b6c04d3c92e9164a209e9079.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/22/4b1c414824d7452485a4e305873db947.png [63d8ee0c6703432e86ded3c06bd8f1ad.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/22/981f5bce633d445b937d2af2f5069029.png [779963d479334c2ba3ca86e9a20604ae.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/22/c0608a5747cc42bda92b162089e81797.png [715f6bf2a99046d594c2964621a3e156.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/22/c4f01842e5214befb34b2207d3383446.png [b9bd5b896f714a54b1bbe637d0f18127.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/22/251cec3cd24d4da1bd4ca478704a16aa.png
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