贪心的本质是选择每一阶段的局部最优,从而达到全局最优
贪心没有套路,说白了就是常识性推导加上举反例。
贪心算法一般分为如下四步:
class Solution { public int findContentChildren(int[] g, int[] s) { Arrays.sort(g); Arrays.sort(s); int start=0; for(int i=0;i<s.length;i++) { if(start<g.length&&s[i]>=g[start]) { start++; } } return start; } }
class Solution { public int wiggleMaxLength(int[] nums) { int pre=0; int cur=0; int count=1; for(int i=0;i<nums.length-1;i++) { cur=nums[i+1]-nums[i]; if(cur>0&&pre<=0||cur<0&&pre>=0) { count++; pre=cur; } } return count; } }
class Solution { public int maxSubArray(int[] nums) { int result=Integer.MIN_VALUE; int count=0; for(int i=0;i<nums.length;i++) { count+=nums[i]; if(count>result) result=count; if(count<=0) count=0; } return result; } }
class Solution { public int maxProfit(int[] prices) { int max=0; for(int i=0;i<prices.length-1;i++) { if(prices[i+1]-prices[i]>0) { max+=prices[i+1]-prices[i]; } } return max; } }