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     PHP堆栈实现
    
        
    
        
     
      1、实现一个MinStack
     
        
     
                            #pragma once                <?php                #define MAX_VALUE 100                typedef struct MinStack {                    int array[MAX_VALUE];                    int top;                } MinStack;                void Init(MinStack *pMs) {                    pMs->top = 0;                }                void Push(MinStack *pMs, int data) {                    int min = data;                    if (pMs->top != 0 && pMs->array[pMs->top - 1] < min) {                        min = pMs->array[pMs->top - 1];                    }                    pMs->array[pMs->top++] = data;                    pMs->array[pMs->top++] = min;                }                void Pop(MinStack *pMs) {                    pMs->top -= 2;                }                int Min(MinStack *pMs) {                    return pMs->array[pMs->top - 1];                }                int Top(MinStack *pMs) {                    return pMs->array[pMs->top - 2];                }                void test1() {                    MinStack ms;                    Init(&ms);                    $arr = array(3, 2, 5, 6, 8, 3, 1, 9);                    foreach ($arr as $i => $val) {                        Push(&ms, $val);                    }                    echo Min(&ms) . " ";                    Pop(&ms);                    echo Min(&ms) . " ";                    Pop(&ms);                    echo Min(&ms) . " ";                }                    
    
    
    
    
        
     
      2、改进方法
     
        
     
            
      方法1：使用一个栈实现交叉存放数据        
     
        
     
            
      方法2：使用两个栈实现更高效的操作        
     
    
    
    
    
        
     
      3、其他技术问题
     
        
     
      使用两个栈实现队列
     
        
     
            <?php            class Solution {                private Stack stack1;                private Stack stack2;                public void push(int node) {                    stack1.push($node);                }                public int pop() {                    if (stack2.isEmpty()) {                        while (!stack1.isEmpty()) {                            stack2.push(stack1.pop());                        }                    }                    return stack2.pop();                }            }            </?php        
    
    
    
    
        
     
      4、字符串数组运算示例
     
        
     
            $str = array("2", "4", "+", "9", "*");            $result = Solution::evalRPN($str);            var_dump($result);        
    
    
   

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