leetcode二期
标准
语言
地址
思路
注释写好
代码done
15
// c with stl(c++)
// 15
// https://leetcode-cn.com/problems/3sum/
// 先排序，然后找，符合的就加入答案
class Solution {
public:
vector<vector<int>> threeSum(vector<int>& nums) {
vector<vector<int>> res;
int NUM = nums.size();
if(NUM < 3)
return res;
sort(nums.begin(), nums.end());
int i,j,k, need, a, before=-111111;
for(i=0; i <NUM -2; i++){
need = -nums[i];
if(before == -need)
continue;
else
before = -need;
j = i+1;
k = NUM-1;
while(j<k){
if(nums[j]+nums[k] > need){
a = nums[k];
while(nums[k] ==a && k>j)
k--;
}
else if(nums[j]+nums[k] < need){
a = nums[j];
while(nums[j] ==a && j<k)
j++;
}
else{
vector<int> temp{nums[i],nums[j],nums[k]};
res.push_back(temp);
a = nums[k];
while(nums[k] ==a && k>j)
k--;
a = nums[j];
while(nums[j] ==a && k>j)
j++;
}
}
}
return res;
}
};
81
// c with stl(c++)
// 81
// https://leetcode-cn.com/problems/search-in-rotated-sorted-array-ii/
// 先分为两段，分别找，找到返回
class Solution {
public:
bool bisearch(vector<int>& nums,int low,int high, int aim){
int mid;
while(low <= high){
mid = (low +high)/2;
if(nums[mid]== aim)
return true;
else if(nums[mid] > aim)
high = mid -1;
else if(nums[mid] < aim){
low = mid +1;
}
}
return false;
}
bool search(vector<int>& nums, int target) {
int start=0;
int size = nums.size();
while((start<size-1) && (nums[start] <= nums[start+1]))
start++;
return bisearch(nums, 0,start, target)||bisearch(nums, start+1,size-1, target);
}
};
35
// c with stl(c++)
// 35
// https://leetcode-cn.com/problems/search-insert-position/
class Solution {
public:
int searchInsert(vector<int>& nums, int target) {
int high = nums.size()-1;
int low = 0,mid;
while(high >= low){
mid = (low +high)/2;
if( nums[mid] ==target)
return mid;
else if( nums[mid] <target)
low = mid+1;
else
high = mid-1;
}
return low;
}
};
33
// c with stl(c++)
// 33
// https://leetcode-cn.com/problems/search-in-rotated-sorted-array/
class Solution {
public:
int bisearch(vector<int>& nums, int low, int high, int target) {
int mid;
while(high >= low){
mid = (low +high) /2;
if( nums[mid] == target)
return mid;
else if( nums[mid] <target)
low = mid+1;
else
high = mid-1;
}
return -1;
}
int inside(vector<int>& nums,int left, int right, int target){
if(left>right)
return -1;
int mid = (left + right)/2;
if(target == nums[mid])
return mid;
if((target > nums[mid]) && (nums[right] >=target))
return bisearch(nums, mid+1, right, target);
if( (target >= nums[left]) && (target < nums[mid]) )
return bisearch(nums, left, mid -1, target);
if( nums[mid] < nums[left])
return inside( nums, left,mid-1, target);
else
return inside( nums, mid +1 , right, target);
}
int search(vector<int>& nums, int target) {
return inside(nums, 0, nums.size()-1, target);
}
};
153
// c with stl(c++)
// 153
// https://leetcode-cn.com/problems/find-minimum-in-rotated-sorted-array/
class Solution {
public:
int inside(vector<int>& nums, int left, int right){
if(nums[left] <=nums[right])
return nums[left];
int mid = (left +right)/2;
if( nums[left] <= nums[mid]){
return inside(nums, mid+1, right);
}else{
return inside(nums, left, mid);
}
}
int findMin(vector<int>& nums) {
return inside(nums, 0, nums.size() -1);
}
};
70
// c with stl(c++)
// 70
// https://leetcode-cn.com/problems/climbing-stairs/
// 用一个数组存1到n阶的方法，然后动态规划？也可以用递归，但是递归比较慢比较耗内存
class Solution {
public:
int climbStairs(int n) {
int dp[n+1];
dp[0] = 1;
dp[1] = 1;
for(int i =2; i <=n; i++){
dp[i] = dp[i-1] + dp[i-2];
}
return dp[n];
}
};
154
// c with stl(c++)
// 154
// https://leetcode-cn.com/problems/find-minimum-in-rotated-sorted-array-ii/
// 二分，递归
class Solution {
public:
int inside(vector<int>& nums, int left, int right){
// cout<< "IN";
// cout<< '(';
// cout<< left ;
// cout<< '-';
// cout<< right ;
// cout<< ')';
int val_l = nums[left] ;
int val_r = nums[right] ;
if( left+1 >= right)
return (val_l > val_r)? val_r: val_l ;
int mid = (left +right)/2 ;
int val_m = nums[mid] ;
if(val_l < val_r)
return val_l;
if(val_l < val_m)
return inside( nums, mid, right);
if(val_m < val_r)
return inside( nums, left, mid);
// cout << "flat";
// int i = left ;
// while((i< right-1) && (nums[i] <= nums[i+1])){
// i++;
// }
// // cout << i;
// if( i == right ){
// i = left-1;
// }
// return nums[i+1];
int min_l = inside(nums, left, mid);
int min_r = inside(nums, mid, right);
return (min_r < min_l)? min_r: min_l;
}
int findMin(vector<int>& nums) {
return inside(nums, 0, nums.size()-1);
}
};
263
// c with stl(c++)
// 263
// https://leetcode-cn.com/problems/ugly-number/
// 分别去掉 n 中的质因数2，3，5，然后判断
class Solution {
public:
bool isUgly(int n) {
if((n == -2147483648)||(n==0))
return false;
while(n%2 ==0)
n /=2;
while(n%3 ==0)
n /=3;
while(n%5 ==0)
n /=5;
if(n==1)
return true;
return false;
}
};
56
// c with stl(c++)
// 56
// https://leetcode-cn.com/problems/merge-intervals/
// 先排序，然后合并
class Solution {
public:
bool judge(vector<int>& i1, vector<int>& i2){
if(i1[1] >= i2[0])
return true;
return false;
}
vector<vector<int>> merge(vector<vector<int>>& intervals) {
int size = intervals.size();
sort(intervals.begin(), intervals.end());
// for(int i = 0; i <size; i++){
// cout<< intervals[i][0];
// cout<< ',';
// cout<< intervals[i][1] << endl;
// }
vector< vector<int>> res;
for(int i = 0; i< size; ){
int j = i+1;
int max = intervals[i][1];
while((j < size) && ( intervals[j][0] <= max)){
(max<intervals[j][1])?(max = intervals[j][1]):1;
j++;
}
res.push_back({intervals[i][0], max});
i = j;
}
return res;
}
};
264
// c with stl(c++)
// 264
// https://leetcode-cn.com/problems/ugly-number-ii/
// 3指针
class Solution {
public:
int nthUglyNumber(int n) {
int dp[n+1];
if(n <=3)
return n;
dp[1] = 1;
int i=1, j =1, k =1;
int count =2;
while(count<= n ){
int min= dp[i]*2;
if(dp[j]*3 <= min)
min =dp[j]*3;
if(dp[k]*5 <= min)
min =dp[k]*5;
dp[count] = min;
while(dp[i]*2 <= min)
i++;
while(dp[j]*3 <= min)
j++;
while(dp[k]*5 <= min)
k++;
count++;
}
return dp[n];
}
};
539
// c with stl(c++)
// 539
// https://leetcode-cn.com/problems/minimum-time-difference/
// 先排序，然后合并
#include <algorithm>
class Solution {
public:
int getnum(string what){
string min(what,0,2);
string sec(what,3,2);
// cout<< min<<'#'<<sec;
return stoi(min)*60 +stoi(sec);
}
int findMinDifference(vector<string>& timePoints) {
int size = timePoints.size();
if(size >1440 )
return 0;
vector<int> res;
int temp;
for(int i = 0; i<size; i++){
temp = getnum( timePoints.back());
timePoints.pop_back();
res.push_back(temp);
}
sort(res.begin(), res.end());
int last = res[size-1];
for(int i = 1; i< size; i++){
res[size - i] = res[size - i] -res[size - i-1];
}
res[0] = res[0]+ 1440 -last;
sort(res.begin(), res.end());
return res[0];
}
};
now
没done
日志
本文写于2021年3月11日，后续会不断更新，目前是用c++（带stl的c）来做题。
4.8 写了5道，主要是二分法的题目
4.9 写了两题
4.10 写了一题
4.11 write 2
