前置知识

构建一个差分数组

void func(int * lb1,int len)
{int * lb2=new int [len];lb2[0]=lb1[0];for (int i=1;i<len;i++)lb2[i]=lb1[i]-lb1[i-1];
}

操作一个连续区间

void func(int * lb,int len1,int begin,int len2,int x)
{lb[begin]+=x;if (begin+len2<len1)lb[begin+len2]-=x;
}

练习习题

1094. 拼车

class Solution {
public:bool carPooling(vector<vector<int>>& trips, int capacity) {int lb[1001] {};for (int i=0;i<trips.size();i++){lb[trips[i][1]]+=trips[i][0];lb[trips[i][2]]-=trips[i][0];}int count=0;for (int i=0;i<1001;i++){count+=lb[i];if (count>capacity) return false;}return true;}
};

1109. 航班预订统计

class Solution {
public:vector<int> corpFlightBookings(vector<vector<int>>& bookings, int n) {int * lb=new int [n+1];for (int i=0;i<n+1;i++) lb[i]=0;for (int i=0;i<bookings.size();i++){lb[bookings[i][0]-1]+=bookings[i][2];lb[bookings[i][1]]-=bookings[i][2];}vector<int> result(n,0);result[0]=lb[0];for (int i=1;i<n;i++)result[i]=result[i-1]+lb[i];delete [] lb;return result;}
};

1450. 在既定时间做作业的学生人数

class Solution {
public:int busyStudent(vector<int>& startTime, vector<int>& endTime, int queryTime) {int time[1000] {};for (int i=0;i<startTime.size();i++){time[startTime[i]-1]+=1;if (endTime[i]<1000) time[endTime[i]]-=1;}for (int i=1;i<1000;i++)time[i]=time[i-1]+time[i];return time[queryTime-1];}
};

2406. 将区间分为最小组数

class Solution {
public:int minGroups(vector<vector<int>>& intervals) {//1e6是双精度浮点数int lb[int(1e6+1)] {};for (int i=0;i<intervals.size();i++){lb[intervals[i][0]-1]+=1;lb[intervals[i][1]]-=1;}int result=lb[0],count=lb[0];for (int i=1;i<1e6;i++){count=count+lb[i];if (count>result) result=count;}return result;}
};

2381. 字母移位II

class Solution {
public:string shiftingLetters(string s, vector<vector<int>>& shifts) {int * lb1=new int [s.size()+1];for (int i=0;i<s.size()+1;i++) lb1[i]=0;for (int i=0;i<shifts.size();i++){int x=shifts[i][2]==1?1:-1;lb1[shifts[i][0]]+=x;lb1[shifts[i][1]+1]-=x;}int * lb2=new int [s.size()];lb2[0]=lb1[0];for (int i=1;i<s.size();i++)lb2[i]=lb2[i-1]+lb1[i];string result;for (int i=0;i<s.size();i++){int x=lb2[i];x+=26*1e5;x%=26;if (s[i]+x<='z') result+=char(s[i]+x);else result+=char(s[i]+x-26);}delete [] lb1;delete [] lb2;return result;}
};

2772. 使数组中的所有元素都等于零

class Solution {
public:bool checkArray(vector<int> &nums, int k) {int * lb=new int [nums.size()];for (int i=0;i<nums.size();i++) lb[i]=0;lb[0]=nums[0];for (int i=1;i<nums.size();i++)lb[i]=nums[i]-nums[i-1];for (int i=0;i<nums.size()-k;i++){if (lb[i]<0) return false;lb[i+k]+=lb[i];}for (int i=nums.size()-k+1;i<nums.size();i++)if (lb[i]!=0) return false;delete [] lb;return true;}
};