Simple type
1
70. Climbing stairs
Suppose you are climbing stairs. It takes n steps to reach the top of the building.
You can climb 1 or 2 steps at a time. How many different ways can you climb to the top of the building?
Note: The given n is a positive integer.
Example 1:
Input: 2
Output: 2
Explanation: There are two ways to climb to the top of the building.
- Tier 1 + Tier 1
- 2nd order
Example 2:
Input: 3
Output: 3
Explanation: There are three ways to climb to the top of the building.
3. Level 1 + Level 1 + Level 1
4. Level 1 + Level 2
5. Level 2 + Level 1
class Solution {
public int climbStairs(int n) {
if(n<3)
return n;
int one = 1;
int two = 2;
int next = 0;
for(int i=2;i<n;i++){
next=one+two;
one=two;
two=next;
}
return next;
}
}
2
198. Fighting at home
You are a professional thief and plan to steal houses along the street. There is a certain amount of cash hidden in each room. The only limiting factor that affects your theft is that the neighboring houses are equipped with an interconnected anti-theft system. If two neighboring houses are hacked into the same night, the system will automatically call .
Given a non-negative integer array representing the amount of money stored in each house, calculate the maximum amount you can steal without touching the alarm device.
Example 1:
Input: [1,2,3,1]
Output: 4
Explanation: Theft of house 1 (amount = 1), then theft of house 3 (amount = 3).
The maximum amount stolen = 1 + 3 = 4.
Example 2:
Input: [2,7,9,3,1]
Output: 12
Explanation: Theft of house 1 (amount = 2), theft of house 3 (amount = 9), and then theft of house 5 (amount = 1).
The maximum amount stolen = 2 + 9 + 1 = 12.
class Solution {
public int rob(int[] nums) {
if(nums.length==0)
return 0;
if(nums.length==1)
return nums[0];
int one = nums[0];
int two = Math.max(nums[0],nums[1]);
int next = Math.max(one,two);
for(int i=2;i<nums.length;i++){
next = Math.max(one+nums[i],two);
one=two;
two=next;
}
return next;
}
}
3
213. Family Fight II
You are a professional thief and plan to steal houses along the street, each room contains a certain amount of cash. All houses in this place are in a circle, which means that the first house and the last house are next to each other. At the same time, the neighboring houses are equipped with an interconnected anti-theft system. If two neighboring houses are broken into by a thief on the same night, the system will automatically call the police.
Given a non-negative integer array representing the amount of money stored in each house, calculate the maximum amount you can steal without touching the alarm device.
Example 1:
Input: [2,3,2]
Output: 3
Explanation: You cannot steal house 1 (amount = 2) first, and then house 3 (amount = 2) because they are adjacent.
Example 2:
Input: [1,2,3,1]
Output: 4
Explanation: You can steal house 1 (amount = 1) first, and then house 3 (amount = 3).
The maximum amount stolen = 1 + 3 = 4.
class Solution {
public int rob(int[] nums) {
int len = nums.length;
if(len==0)
return 0;
if(len==1)
return nums[0];
int one1=nums[0];
int two1=Math.max(nums[0],nums[1]);
int next1=Math.max(one1,two1);
for(int i=2;i<len-1;i++){
next1=Math.max(one1+nums[i],two1);
one1=two1;
two1=next1;
}
int next2=nums[1];
if(len>3){
int one2=nums[1];
int two2=Math.max(nums[1],nums[2]);
next2=Math.max(one2,two2);
for(int i=3;i<len;i++){
next2=Math.max(one2+nums[i],two2);
one2=two2;
two2=next2;
}
}
return Math.max(next1,next2);
}
}
4
