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前言

差分数组的主要适用场景是频繁对原始数组的某个区间的元素进行增减
这里提供一个工具类方便大家使用

差分数组工具类

class Difference{private int[] diff;public Difference(int[] nums){diff = new int[nums.length];diff[0] = nums[0];for(int i = 1; i < nums.length; i ++){diff[i] = nums[i] - nums[i-1];}}public void increment(int low, int high, int val){diff[low] += val;if(high < diff.length-1){diff[high+1] -= val;}}public int[] result(){int[] res = new int[diff.length];res[0] = diff[0];for(int i = 1; i < diff.length; i ++){res[i] = res[i-1] + diff[i];}return res;}
}

一、力扣370. 区间加法

class Solution {public int[] getModifiedArray(int length, int[][] updates) {int[] res = new int[length];Difference diff = new Difference(res);for(int i = 0; i < updates.length; i ++){diff.increment(updates[i][0],updates[i][1],updates[i][2]);}res = diff.result();return res;}
}
class Difference{private int[] diff;public Difference(int[] nums){diff = new int[nums.length];diff[0] = nums[0];for(int i = 1; i < nums.length; i ++){diff[i] = nums[i] - nums[i-1];}}public void increment(int low, int high, int val){diff[low] += val;if(high < diff.length-1){diff[high+1] -= val;}}public int[] result(){int[] res = new int[diff.length];res[0] = diff[0];for(int i = 1; i < diff.length; i ++){res[i] = res[i-1] + diff[i];}return res;}
}

二、力扣1109. 航班预订统计

class Solution {public int[] corpFlightBookings(int[][] bookings, int n) {int[] res = new int[n];Difference diff = new Difference(res);for(int i = 0; i < bookings.length; i ++){diff.increase(bookings[i][0]-1,bookings[i][1]-1,bookings[i][2]);}res = diff.result();return res;}
}
class Difference{private int[] diff;public Difference(int[] nums){diff = new int[nums.length];diff[0] = nums[0];for(int i = 1; i < nums.length; i ++){diff[i] = nums[i] - nums[i-1];}}public void increase(int low,int high, int val){diff[low] += val;if(high + 1 < diff.length){diff[high+1] -= val;}}public int[] result(){int[] res = new int[diff.length];res[0] = diff[0];for(int i = 1; i < diff.length; i ++){res[i] = res[i-1] + diff[i];}return res;}
}

三、力扣1094. 拼车

class Solution {public boolean carPooling(int[][] trips, int capacity) {int[] res = new int[1001];Difference diff = new Difference(res);for(int i = 0; i < trips.length; i ++){diff.increase(trips[i][1],trips[i][2]-1,trips[i][0]);}res = diff.result();for(int i = 0; i < res.length; i ++){if(res[i] > capacity){return false;}}return true;}
}
class Difference{private int[] diff;public Difference(int[] nums){diff = new int[nums.length];diff[0] = nums[0];for(int i = 1; i < nums.length; i ++){diff[i] = nums[i] - nums[i-1];}}public void increase(int low, int high, int val){diff[low] += val;if(high + 1 < diff.length){diff[high+1] -= val;}}public int[] result(){int[] res = new int[diff.length];res[0] = diff[0];for(int i = 1; i < diff.length; i ++){res[i] = res[i-1] + diff[i];}return res;}
}