day31打卡

第八部分 贪心算法

1. 理论基础

2. 分发饼干

var findContentChildren = function(g, s) {
    g.sort((a, b) => a - b);
    s.sort((a, b) => a - b);
    const m = g.length, n = s.length;
    let count = 0;
    for (let i = 0, j = 0; i < m && j < n; i++, j++) {
        while (j < n && g[i] > s[j]) {
            j++;
        }
        if (j < n) {
            count++;
        }
    }
    return count;
};

3. 摆动序列

var wiggleMaxLength = function(nums) {
    const n = nums.length;
    if (n < 2) return n;
    const up = new Array(n).fill(0);
    const down = new Array(n).fill(0);
    up[0] = down[0] = 1;
    for (let i = 1; i < n; i++) {
        if (nums[i] > nums[i - 1]) {
            up[i] = Math.max(up[i - 1], down[i - 1] + 1);
            down[i] = down[i - 1];
        } else if (nums[i] < nums[i - 1]) {
            up[i] = up[i - 1];
            down[i] = Math.max(up[i - 1] + 1, down[i - 1]);
        } else {
            up[i] = up[i - 1];
            down[i] = down[i - 1];
        }
    }
    return Math.max(up[n - 1], down[n - 1]);
};

4. 最大子序和

var maxSubArray = function(nums) {
    let pre = 0, maxAns = nums[0];
    nums.forEach((x) => {
        pre = Math.max(pre + x, x);
        maxAns = Math.max(maxAns, pre);
    });
    return maxAns;
};