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leetcode_java/src/main/java/LeetCodeJava/DynamicProgramming/HouseRobber2.java
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| package LeetCodeJava.DynamicProgramming; | ||
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| // https://leetcode.com/problems/house-robber-ii/ | ||
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| import java.util.Arrays; | ||
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| public class HouseRobber2 { | ||
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| // V0 | ||
| // IDEA : DP, LC 198 | ||
| // https://github.com/yennanliu/CS_basics/blob/master/leetcode_python/Dynamic_Programming/house-robber-ii.py | ||
| public int rob(int[] nums) { | ||
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| if (nums.length == 1) { | ||
| return nums[0]; | ||
| } | ||
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| if (nums.length == 2) { | ||
| return Math.max(nums[0], nums[1]); | ||
| } | ||
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| // Consider the scenario where the first and last houses are adjacent | ||
| // so either | ||
| // -> we rob first and last 2 idx | ||
| // -> or rob 2nd and last idx | ||
| int max1 = robRange(nums, 0, nums.length - 2); | ||
| int max2 = robRange(nums, 1, nums.length - 1); | ||
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| return Math.max(max1, max2); | ||
| } | ||
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| // NOTE !!! define robRange(int[] nums, int start, int end) | ||
| // with start, end idx | ||
| public int robRange(int[] nums, int start, int end) { | ||
| int[] dp = new int[nums.length]; | ||
| dp[start] = nums[start]; | ||
| dp[start + 1] = Math.max(nums[start], nums[start + 1]); | ||
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| for (int i = start + 2; i <= end; i++) { | ||
| dp[i] = Math.max(dp[i - 1], dp[i - 2] + nums[i]); | ||
| } | ||
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| return dp[end]; | ||
| } | ||
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| // V1 | ||
| // https://leetcode.com/problems/house-robber-ii/solutions/4844002/beats-100-simple-to-understand/ | ||
| public int robber(int[] nums) { | ||
| int n=nums.length; | ||
| int prev=nums[0]; | ||
| int prev2=0; | ||
| for(int i=1;i<n;i++){ | ||
| int pick=nums[i]; | ||
| if(i>1) pick+=prev2; | ||
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| int notpick=prev; | ||
| int curr=Math.max(pick, notpick); | ||
| prev2=prev; | ||
| prev=curr; | ||
| } | ||
| return prev; | ||
| } | ||
| public int rob_2(int[] nums) { | ||
| int n=nums.length; | ||
| if(n==1) return nums[0]; | ||
| int[] ind1=new int[n-1]; | ||
| int[] ind2=new int[n-1]; | ||
| for(int i=0;i<n-1;i++){ | ||
| ind1[i]=nums[i+1]; | ||
| } | ||
| for(int i=0;i<n-1;i++){ | ||
| ind2[i]=nums[i]; | ||
| } | ||
| int a=robber(ind1); | ||
| int b=robber(ind2); | ||
| return Math.max(a, b); | ||
| } | ||
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| // V2 | ||
| // https://leetcode.com/problems/house-robber-ii/solutions/4055922/beautiful-hashmap-handling-subproblems/ | ||
| // public int rob_3(int[] nums) { | ||
| // int ind=nums.length-1; | ||
| // HashMap<Pair,Integer> map=new HashMap<>(); | ||
| // if(ind==0) | ||
| // return nums[0]; | ||
| // else | ||
| // return Math.max(f(ind-1,nums,0,map),f(ind,nums,nums[ind],map)); | ||
| // } | ||
| // public static int f(int i,int nums[],int curr,HashMap<Pair,Integer> map){ | ||
| // Pair key=new Pair(i,curr); | ||
| // if(map.containsKey(key)) | ||
| // return map.get(key); | ||
| // if(i<0) | ||
| // return 0; | ||
| // if(i==0){ | ||
| // if(curr==0) | ||
| // return nums[0]; | ||
| // else | ||
| // return 0; | ||
| // } | ||
| // int take=f(i-2,nums,curr,map)+nums[i]; | ||
| // int nottake=f(i-1,nums,curr,map); | ||
| // map.put(key,Math.max(take,nottake)); | ||
| // return Math.max(take,nottake); | ||
| // } | ||
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| } |
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