原題

思路

每一個新元素被 pop，他的出現次數，是他前一個出現相同元素的 次數 + 1
注意節約資源。

程式碼

var FreqStack = function() {
    this.stack = [];
    this.disc = []; // 字典 幫助判斷
};

/** 
 * @param {number} x
 * @return {void}
 */
FreqStack.prototype.push = function(x) {
    let count = 1;
    if(this.disc.indexOf(x) < 0) { // 不存在
        this.disc.push(x);
    } else { // 之前確實有這個元素 從後向前找
        let len = this.stack.length;
        for(let i = len -1; i >= 0; --i) {
            if(this.stack[i].value === x) {
                count += this.stack[i].count;
                break;
            }
        }
    }
    
    this.stack.push({
        value: x,
        count
    });
};

/**
 * @return {number}
 */
FreqStack.prototype.pop = function() {
    let list = [];
    let max = 0;
    let len = this.stack.length;
    let toRemoveIndex = -1;
    for(let i = len - 1; i >= 0; --i) {
        let obj = this.stack[i];
        if(obj.count > max) {
            max = obj.count;
            list = [obj.value];
            toRemoveIndex = i;
        }
    }
    this.stack.splice(toRemoveIndex, 1);
    return list[0];
};

/** 
 * Your FreqStack object will be instantiated and called as such:
 * var obj = Object.create(FreqStack).createNew()
 * obj.push(x)
 * var param_2 = obj.pop()
 */
複製程式碼