leetcode: 251. Expanding 2D Vectors

题目来源

• leetcode：251-VIP. 展开二维向量

题目描述

题目解析

class Vector2D  {
    
    std::vector<std::vector<int>> m;
    int row;
    int col; //迭代器光标位置
    bool canUse; //Whether the position pointed to by the cursor has already been used

public:
    Vector2D(std::vector<std::vector<int>> v){
    
        m = std::move(v);
        row = 0, col = -1;
        canUse = true; //认为[0, -1]使用过
        has_next();
    }

    bool  has_next(){
    
        if(row == m.size()){
    
            return false; //Exceeded terminating line
        }

        if(!canUse){
     //The current number has not been used yet
            return true;
        }

        // (row, col) 被使用过了, Going to the next one
        if(col == m[row].size() - 1){
    
            col = 0;
            do{
     //跳过空行
                row++;
            }while (row < m.size() && m[row].empty());
        }else{
    
            col++;
        }

        // 新的(row, col)
        if(row != m.size()){
    
            canUse = false;
            return true;
        }else{
    
            return false; //to the end line
        }
    }
    int next(){
    
        int ans = m[row][col];
        canUse = true;
        has_next();
        return ans;
    }

};