//思路在剑指offer书的图里，很容易理解。这里由于c没有API，所以要先定义Stack结构体，不像JavaScript有已经定义好的结构体。并且一些如弹入弹出的操作，也需要自己定义。
1 typedef struct {
2 int* stk;
3 int stkSize;
4 int stkCapacity;
5 } Stack;
6
7 Stack* stackCreate(int cpacity) {
8 Stack* ret = malloc(sizeof(Stack));
9 ret->stk = malloc(sizeof(int) * cpacity);
10 ret->stkSize = 0;
11 ret->stkCapacity = cpacity;
12 return ret;
13 }
14
15 void stackPush(Stack* obj, int value) {
16 obj->stk[obj->stkSize++] = value;
17 }
18
19 void stackPop(Stack* obj) {
20 obj->stkSize--;
21 }
22
23 int stackTop(Stack* obj) {
24 return obj->stk[obj->stkSize - 1];
25 }
26
27 bool stackEmpty(Stack* obj) {
28 return obj->stkSize == 0;
29 }
30
31 void stackFree(Stack* obj) {
32 free(obj->stk);
33 }
34
35 typedef struct {
36 Stack* inStack;
37 Stack* outStack;
38 } CQueue;
39
40 CQueue* cQueueCreate() {
41 CQueue* ret = malloc(sizeof(CQueue));
42 ret->inStack = stackCreate(10000);
43 ret->outStack = stackCreate(10000);
44 return ret;
45 }
46
47 void in2out(CQueue* obj) {
48 while (!stackEmpty(obj->inStack)) {
49 stackPush(obj->outStack, stackTop(obj->inStack));
50 stackPop(obj->inStack);
51 }
52 }
53
54 void cQueueAppendTail(CQueue* obj, int value) {
55 stackPush(obj->inStack, value);
56 }
57
58 int cQueueDeleteHead(CQueue* obj) {
59 if (stackEmpty(obj->outStack)) {
60 if (stackEmpty(obj->inStack)) {
61 return -1;
62 }
63 in2out(obj);
64 }
65 int x = stackTop(obj->outStack);
66 stackPop(obj->outStack);
67 return x;
68 }
69
70 void cQueueFree(CQueue* obj) {
71 stackFree(obj->inStack);
72 stackFree(obj->outStack);
73 }
