算法：栈模拟递归之求和

小鱼儿 2023-02-16 00:42 49阅读 0赞

# C++ #

#include <stack>
    #include <cstdio>
    using namespace std;
    
    int sum(int num){
        
        if(num == 0){
        
            return 0;
        }
    
        return num + sum(num - 1);
    }
    
    
    int sum_for(int num){
        
        if (num == 0){
        
            return 0;
        }
    
        int sum = 0;
        for(int i = 1; i <= num ; i++){
        
            sum += i;
        }
    
        return sum;
    }
    
    
    int sum_stack(int num){
        
        std::stack<int> stack;
        stack.emplace(num);
    
        int res = 0, data = 0;
        while (!stack.empty()){
        
            data = stack.top();
            if(data == 0){
        
                break;
            }else{
        
                res += data;
                stack.push(data - 1);
            }
        }
    
        return res;
    }
    
    
    int main(int argc,char **argv){
        
    
        printf("%d\n", sum_for(100));
        printf("%d\n", sum(100));
        printf("%d", sum_stack(100));
    
    
        return 0;
    }

# java #

public static int sum(int num){
        
            if (num == 0){
        
                return 0;
            }
            return num + sum(num - 1);
        }
    
        public static int sumStack(int num){
        
            int res = 0;
            Stack<Integer> stack = new Stack<Integer>();
            stack.push(num);
    
            while (!stack.empty()){
        
                int data = stack.pop();
                if (data == 0){
        
                    res = res + data;
                }else{
        
                    res = res + data;
                    stack.push(data - 1);
                }
            }
    
            return res;
        }
    
    
        public static void main(String[] args){
        
            System.out.println(sum(100));
            System.out.println(sumStack(100));
        }