6136. 算术三元组的数目
class Solution {
public:
int arithmeticTriplets(vector<int>& a, int f) {
int n = a.size();
int ret=0;
for(int i=0;i<n;++i){
for(int j=i+1;j<n;++j){
for(int k = j+1;k<n;++k){
if( a[j]-a[i]==f && a[k]-a[j] ==f ){
++ret;
}
}
}
}
return ret;
}
};6139. 受限条件下可到达节点的数目
class Solution {
public:
int reachableNodes(int n, vector<vector<int>>& e, vector<int>& r) {
vector<vector<int>> ne(n+1);
unordered_map<int,int>m;
for(int x:r){
m[ x ] = 1;
}
for( auto&arr:e ){
if( m[arr[0]]==0 && m[ arr[1] ]==0 ){
ne[ arr[0] ].push_back(arr[1]);
ne[ arr[1] ].push_back(arr[0]);
}
}
int ret = 0;
queue<int> q;
q.push(0);
unordered_map<int,int> v;
while( !q.empty() ){
int tp =q.front();
q.pop();
v[tp] = true;
++ret;
for(int n:ne[tp]){
if( v[n] == 0 ){
v[n]=1;
q.push(n);
}
}
}
return ret;
}
};6137. 检查数组是否存在有效划分
class Solution {
public:
bool validPartition(vector<int>& a) {
int n = a.size();
auto dp = vector<bool>(n+1,false);
dp[0] = true;
if( a[1] == a[0] ){
dp[2] = true;
}
for(int i=3;i<=n;++i){
if(a[i-1] == a[i-2]){
dp[i] = dp[i]||dp[i-2];
}
if( a[i-1] == a[i-2] && a[i-1] == a[i-3]){
dp[i] = dp[i]||dp[i-3];
}
if( a[i-1] == a[i-2]+1 && a[i-2] == a[i-3]+1 ){
dp[i] = dp[i]||dp[i-3];
}
}
return dp[n];
}
};6138. 最长理想子序列
~思路
https://leetcode.cn/problems/longest-ideal-subsequence/solution/by-lfool-afr2/
class Solution {
public:
int longestIdealString(string s, int k) {
int n = s.size();
vector<int> dp(26,0);
for(int i=0;i<n;++i){
int cur = s[i] - 'a';
for(int j=1;j<=k;++j){
if( cur-j>=0){
dp[cur] = std::max<int>(dp[cur],dp[cur-j]);
}
if( cur+j < 26){
dp[cur] = std::max<int>(dp[cur],dp[cur+j]);
}
}
++dp[cur];
}
return *max_element(dp.begin(),dp.end());
}
};
