编程范式：通用的二分查找

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

void *binary_search (void *arr, void *value, int len, int mem, int(*compare)(void *, void *)) {
	int low = 0;
	int high = len-1;
	int mid;
	while(low <= high) {
		mid = (low + high) / 2;
		void* addr = (char*)arr + mid * mem;
		if (compare(addr, value) == 0) {
			return addr;
		}
		else if (compare(addr, value) > 0) {
			high = mid - 1;
		}
		else {
			low = mid + 1;
		}
	}
	return NULL;
}

int cmp_int (void* x, void* y) {
	int *a = (int*)x;
	int *b = (int*)y;
	return *a - *b;
}

int cmp_string (void* x, void* y) {
	char *a = *(char**)x;
	char *b = *(char**)y;
	return strcmp(a, b);
}


int main (int argc, char **argv) {

	//查找整数
	int arr[] = {10, 20, 30, 40, 50, 60, 70, 80, 90, 100};
	int num = 10;
	int value = 10;
	void* ret = binary_search(arr, &value, num, sizeof(int), cmp_int);
	if (ret == NULL) {
		printf("NULL\n");
	}
	else {
		printf("%d\n", *((int*)ret));
	}


	//查找字符串
	char* books[] = {"水浒传", "三国演义", "西游记", "红楼梦"};
	char* book = "三国演义";
	int len = 4;
	void* retStr = binary_search(books, &book, 4, sizeof(char *), cmp_string);
	if (retStr == NULL) {
		printf("NULL\n");
	}
	else {
		printf("%s\n", *((char**)retStr));
	}

	return 0;
}

通用线性查找：

#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#include <string.h>

void *search (void *a, void *value, int len, int size, int(*cmp)(void*, void*)) {
    for (int i = 0; i < len; i++) {
        void *addr = (char *)a + i * size;
        if (cmp(addr, value) == 0) {
            return addr;
        }
    }
    return NULL;
}

int cmp_int(void *x, void *y) {
    return *(int *)x - *(int *)y;
}

int cmp_str(void *x, void *y) {
    return strcmp(*(char **)x, *(char **)y);
}

int main (int argc, char **argv) {
    char *books[] = {"水浒传", "三国演义", "西游记", "红楼梦"};
    char *book = "西游记";
    void *ret_str = search(books, &book, 4, sizeof(char *), cmp_str);
    printf("%s\n", *(char **)ret_str);
    int a[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    int len = 10;
    int value = 5;
    void *ret_int = search(a, &value, len, sizeof(int), cmp_int);
    printf("%d\n", *(int *)ret_int);
    return 0;
}

通用交换函数：

#include <stdio.h>
#include <memory.h>

void swap (void *a, void *b, int size) {
    char tmp[size];
    memcpy(tmp, a, size);
    memcpy(a, b, size);
    memcpy(b, tmp, size);
}

int main (int argc, char **argv) {
    int x = 36, y = 72;
    swap(&x, &y, sizeof(int));
    printf("%d %d\n", x, y);

    double p = 3.1415926, e = 2.7182818;
    swap(&p, &e, sizeof(double));
    printf("%lf %lf\n", p, e);

    char *s1 = strdup("倚天剑");
    char *s2 = strdup("屠龙刀");
    swap(&s1, &s2, sizeof(char *));
    printf("%s %s", s1, s2);
    return 0;
}

通用栈：

#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#include <string.h>

typedef struct {
    int *elem;
    int len;//栈中元素的个数
    int volume;
    int size;
} stack;

void init (stack *s, int size) {
    s->len = 0;
    s->volume = 3;
    s->size = size;
    s->elem = malloc(s->volume * s->size);
}

void push (stack *s, void *value) {
    if (s->len == s->volume) {
        s->volume *= 2;
        s->elem = realloc(s->elem, s->volume * s->size);
    }
    void *addr = (char *)s->elem + s->len * s->size;
    memcpy(addr, value, s->size);
    s->len++;
}

void pop (stack *s, void *value) {
    void *addr = (char *)s->elem + (s->len - 1) * s->size;
    memcpy(value, addr, s->size);
    s->len--;
}

int main (int argc, char **argv) {
    int cards[5] = {3, 7, 1, 2, 4};
    stack s;
    init (&s, sizeof(int));
    for (int i = 0; i < 5; i++) {
        push(&s, &cards[i]);
    }
    for (int i = 0; i < 5; i++) {
        pop(&s, &cards[i]);
    }
    for (int i = 0; i < 5; i++) {
        printf("%d\n", cards[i]);
    }

    char *books[4] = {"西游记", "三国演义", "水浒传", "红楼梦"};
    stack st;
    init(&st, sizeof(char *));
    for (int i = 0; i < 4; i++) {
        char *book = strdup(books[i]);
        push(&st, &book);
    }
    char *name;
    for (int i = 0; i < 4; i++) {
        pop(&st, &name);
        printf("%s\n", name);
        free(name);
    }
}