定义栈的数据结构，要求添加一个 min 函数，能够得到栈的最小元素。 要求函数 min、push 以及 pop 的时间复杂度都是 O(1)。
1 template<typename T> 2 struct MinStackElement 3 { 4 T data; 5 T min; 6 }; 7 8 template<typename T> 9 struct MinStack 10 { 11 MinStack() : pData(NULL), size(0), top(0){} 12 MinStackElement<T>* pData; 13 int size; 14 int top; 15 }; 16 17 template<typename T> 18 void MinStackInitialize(MinStack<T>& s, int maxSize) 19 { 20 MinStackFree(s); 21 s.pData = (MinStackElement<T>*)malloc(maxSize*sizeof(MinStackElement<T>)); 22 memset(s.pData, 0, maxSize*sizeof(MinStackElement<T>)); 23 s.size = maxSize; 24 s.top = 0; 25 } 26 27 template<typename T> 28 void MinStackFree(MinStack<T>& s) 29 { 30 if (s.pData) 31 { 32 free(s.pData); 33 s.pData = nullptr; 34 } 35 36 s.size = 0; 37 s.top = 0; 38 } 39 40 template<typename T> 41 void MinStackPush(MinStack<T>& s, T data) 42 { 43 if (s.size == 0) 44 { 45 printf("Stack is not initialized. "); 46 return; 47 } 48 49 if (s.top == s.size) 50 { 51 printf("Stack is full. "); 52 return; 53 } 54 55 s.pData[s.top].data = data; 56 s.pData[s.top].min = (s.top == 0 ? data : s.pData[s.top - 1].min); 57 if (s.pData[s.top].min > data) 58 { 59 s.pData[s.top].min = data; 60 } 61 62 wcout << L"stack push " << data << endl; 63 s.top++; 64 } 65 66 template<typename T> 67 T MinStackPop(MinStack<T>& s) 68 { 69 if (s.top == 0) 70 { 71 printf("Stack is empty. "); 72 return -1; 73 } 74 75 T data = s.pData[--s.top].data; 76 wcout << L"stack pop " << data << endl; 77 78 return data; 79 } 80 81 template<typename T> 82 T MinStackGetMin(const MinStack<T>& s) 83 { 84 if (s.top == 0) 85 { 86 printf("Stack is empty. "); 87 return 0; 88 } 89 90 T min = s.pData[s.top - 1].min; 91 printf("Min :%d ", min); 92 93 return min; 94 } 95 96 int _tmain(int argc, _TCHAR* argv[]) 97 { 98 int min = 0; 99 MinStack<int> s; 100 101 MinStackPush(s, 9); 102 103 MinStackInitialize(s, 10); 104 MinStackPush(s, 9); 105 MinStackPush(s, 5); 106 MinStackPush(s, 6); 107 MinStackPush(s, 4); 108 MinStackPop(s); 109 MinStackGetMin(s); 110 MinStackPush(s, 3); 111 MinStackPush(s, 8); 112 MinStackPush(s, 2); 113 114 MinStackPop(s); 115 116 MinStackPush(s, 7); 117 MinStackPush(s, 1); 118 119 MinStackGetMin(s); 120 121 MinStackPop(s); 122 MinStackGetMin(s); 123 MinStackPop(s); 124 MinStackGetMin(s); 125 MinStackPop(s); 126 MinStackGetMin(s); 127 MinStackPop(s); 128 MinStackGetMin(s); 129 MinStackPop(s); 130 MinStackGetMin(s); 131 MinStackPop(s); 132 MinStackPop(s); 133 MinStackPop(s); 134 MinStackGetMin(s); 135 136 MinStackFree(s); 137 138 return 0; 139 }
>test.exe
Stack is not initialized.
stack push 9
stack push 5
stack push 6
stack push 4
stack pop 4
Min :5
stack push 3
stack push 8
stack push 2
stack pop 2
stack push 7
stack push 1
Min :1
stack pop 1
Min :3
stack pop 7
Min :3
stack pop 8
Min :3
stack pop 3
Min :5
stack pop 6
Min :5
stack pop 5
stack pop 9
Stack is empty.
Stack is empty.