198 House Robber – Easy



Problem:

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is that adjacent houses have security system connected and it will automatically contact the police if two adjacent houses were broken into on the same night.

Given a list of non-negative integers representing the amount of money of each house, determine the maximum amount of money you can rob tonight without alerting the police.

Thoughts:

For each house, there are two choices, either rob or not rob. And this decision is affecting later choice.

So we need two variables to keep the current max for with current value and without current value.

This is a little bit like DP, but no need to have an array because all previous optimal value doesn’t matter.

Solutions:

class Solution {
    public int rob(int[] nums) {
        int rob = 0;
        int norob = 0;
        for (int i = 0; i < nums.length; i ++) {
            int newRob = norob + nums[i];
            int newNoRob = Math.max(norob, rob);
            rob = newRob;
            norob = newNoRob;
        }
        return Math.max(rob, norob);
    }
}