编写一个函数,实现顺序表的就地逆置,也就是说利用原表的存储空间将顺序表(a1,a2...an)逆置为(an,an-1...a2,a1)。
让我们能想到的是,利用使用三个指针,分别指向开始,中间,结束。元素。通过中间元素实现,开始元素和结束元素的交换,然后,开始元素的指针加一,结束元素的指针减一,这样循环下去,当开始元素的指针不小于中间元素指针时停止。
代码如下:
- #include <stdio.h>
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#include <stdlib.h>
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typedef struct{
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int *base;
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int length;
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} sqlist;
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void reverseSQ(sqlist *l)
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{
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int low = 0, high = l->length - 1;
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int buf, i, count = l->length / 2;
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for(i=0; i<count; i++){
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buf = l->base[low];
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l->base[low++] = l->base[high];
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l->base[high--] = buf;
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}
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}
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void printSQ(sqlist *l)
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{
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int i = 0;
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for(i=0; i<l->length; i++)
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printf("%d ",l->base[i]);
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printf("\n");
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}
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int main(int argc, char *argv[])
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{
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sqlist l;
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int a,i = 0;
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int cnt = 0;
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printf("please input count num:");
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scanf("%d",&cnt);
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l.base = (int *)malloc(sizeof(int) * cnt);
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l.length = 0;
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while(i < cnt){
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scanf("%d",&a);
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l.base[i++] = a;
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l.length++;
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}
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printf("the contents of the sqlist are\n");
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printSQ(&l);
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reverseSQ(&l);
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printf("the contents of the reversed sqlist are\n");
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printSQ(&l);
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free(l.base); //释放内存
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return 0;
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}
运行结果:
peng@ubuntu:~/src/test/c/suanfa/miaoqu$ gcc -Wall 7.1-1.c
peng@ubuntu:~/src/test/c/suanfa/miaoqu$ ./a.out
please input count num:5
1 2 3 4 5
the contents of the sqlist are
1 2 3 4 5
the contents of the reversed sqlist are
5 4 3 2 1
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