剑指offer_机器人的运动范围

题目链接：www.acwing.com/problem/con…

分析

bfs+set

Code

/**
 * @param {number} threshold
 * @param {number} rows
 * @param {number} cols
 * @return {number}
 */
var movingCount = function(threshold, rows, cols) {
    
    if(rows === 0 || cols === 0) return 0;  //特判
    
    function getSum(num){
        let ans = 0;
        while(num){
            ans += num % 10;
            num = Math.floor(num / 10); // 53 /3 ==> 5
        }
        return ans;
    }  
    
    let dx = [-1, 0, 1, 0];
    let dy = [0, 1, 0, -1];
    
    
    //用set保存已经走过的坐标
    let set = new Set(['0,0']);
    //bfs
    const queue = [[0,0]];
    
    let res = 0;
    while(queue.length > 0){
        //弹出队头
        const [x, y] = queue.shift();
        //四个方向遍历
        for(let i = 0; i < 4; i ++){
            let a = x + dx[i];
            let b = y + dy[i];
            
            if (a < 0 || a >= rows || b < 0 || b >= cols || getSum(a) + getSum(b) > threshold || set.has(`${a},${b}`)) {
                    continue;
                }

                res += (getSum(a) + getSum(b));
                set.add(`${a},${b}`);
                queue.push([a, b]);
        }
    }
    
    return set.size;
    
};