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Rob.java
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69 lines (58 loc) · 1.64 KB
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package com.github.algorithm.dp;
public class Rob {
public int rob(int[] nums) {
if (nums == null || nums.length == 0) {
return 0;
}
if (nums.length == 1) {
return nums[0];
}
return Math.max(rob3(nums, 1, nums.length), rob3(nums, 0, nums.length-1));
}
public int rob3(int[] nums, int begin, int end) {
if (end - begin <= 0) {
return 0;
}
if (end == begin+1) {
return nums[begin];
}
int pre2 = nums[begin];
int pre1 = Math.max(nums[begin], nums[begin+1]);
int cur = pre1;
for (int i = begin+2;i < end;i ++) {
cur = Math.max(pre2+nums[i], pre1);
pre2 = pre1;
pre1 = cur;
}
return cur;
}
/**
* dp[i] 表示从开始偷到第i家的最大金额
* 偷i dp[i] = max(dp[i-1], dp[i-2] + nums[i])
* 不偷i dp[i] = dp[i-1]
* dp[0]=nums[0]
* dp[1]=max(nums[0],nums[1])
* @param nums
* @return
*/
public int rob2(int[] nums) {
if (nums == null || nums.length == 0) {
return 0;
}
if (nums.length == 1) {
return nums[0];
}
int[] dp = new int[nums.length];
dp[0] = nums[0];
dp[1] = Math.max(nums[0], nums[1]);
for (int i = 2;i < nums.length;i ++) {
dp[i] = Math.max(dp[i-2]+nums[i], dp[i-1]);
}
return dp[nums.length-1];
}
public static void main(String[] args) {
Rob rob = new Rob();
// rob.rob(new int[]{2,7,9,3,1});
System.out.println(rob.rob(new int[]{1}));
}
}