大家好,又见面了,我是你们的朋友全栈君。
int[] diff = new int[nums.length];
// 构造差分数组
diff[0] = nums[0];
for (int i = 1; i < nums.length; i++) {
diff[i] = nums[i] - nums[i - 1];
}
2.根据差分树组反推原数组(res):res[0]=diff[0],res[i]=res[i-1]+diff[i]
int[] res = new int[diff.length];
// 根据差分数组构造结果数组
res[0] = diff[0];
for (int i = 1; i < diff.length; i++) {
res[i] = res[i - 1] + diff[i];
}
3.这样构造差分数组 diff,就可以快速进⾏区间增减的操作,如果你想对区间 nums[i…j] 的元素全部加3,那么只需要让 diff[i] += 3,然后再让 diff[j+1] -= 3 即可:
// 差分数组⼯具类
class Difference {
// 差分数组
private int[] diff;
/* 输⼊⼀个初始数组,区间操作将在这个数组上进⾏ */
public Difference(int[] nums) {
assert nums.length > 0;//若是空数组则抛异常
diff = new int[nums.length];
// 根据初始数组构造差分数组
diff[0] = nums[0];
for (int i = 1; i < nums.length; i++) {
diff[i] = nums[i] - nums[i - 1];
}
}
/* 给闭区间 [i,j] 增加 val(可以是负数)*/
public void increment(int i, int j, int val) {
diff[i] += val;
if (j + 1 < diff.length) {
diff[j + 1] -= val;
}
}
/* 返回结果数组 */
public int[] result() {
int[] res = new int[diff.length];
// 根据差分数组构造结果数组
res[0] = diff[0];
for (int i = 1; i < diff.length; i++) {
res[i] = res[i - 1] + diff[i];
}
return res;
}
}
int[] getModifiedArray(int length, int[][] updates) {
// nums 初始化为全 0
int[] nums = new int[length];
// 构造差分解法
Difference df = new Difference(nums);
for (int[] update : updates) {
int i = update[0];
int j = update[1];
int val = update[2];
df.increment(i, j, val);
}
return df.result();
}
// 差分数组⼯具类
class Difference {
// 差分数组
private int[] diff;
//构建拆分数组
public Difference(int nums[]){
assert nums.length >0;
diff=new int[nums.length];
diff[0]=nums[0];
for(int i=1;i<nums.length;i++){
diff[i]=nums[i]-nums[i-1];
}
}
/* 给闭区间 [i,j] 增加 val(可以是负数)*/
public void increment(int i, int j, int val) {
diff[i]+=val;
if(j+1<diff.length){
diff[j+1]-=val;
}
}
public int[] reslut(){
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;
}
}
class Solution {
public int[] corpFlightBookings(int[][] bookings, int n) {
int nums[]=new int [n];
Difference df=new Difference(nums);
for(int arr[]:bookings){
int i=arr[0]-1;
int j=arr[1]-1;
int val=arr[2];
df.increment(i,j,val);
}
return df.reslut();
}
}
class Solution {
public int[] corpFlightBookings(int[][] bookings, int n) {
int nums[]=new int [n];
for(int arr[]:bookings){
int i=arr[0]-1;
int j=arr[1]-1;
int val=arr[2];
nums[i]+=val;
if(j+1<n){
nums[j+1]-=val;
}
}
for (int i = 1; i < n; i++) {
nums[i] += nums[i - 1];
}
return nums;
}
}
class Solution {
public boolean carPooling(int[][] trips, int capacity) {
int max=0;
//计算此次中到达最远的栈的编号
for(int[] trip : trips){
max = Math.max(trip[2], max);
}
//nums看做差分数组
int nums[]=new int [max];
//遍历信息 构建差分树组
for(int trip[]:trips){
int val=trip[0];
//处理第一次人数大于乘载量的情况
if(capacity<val)
return false;
//路程是trip[1]-trip[2]-1
int i=trip[1];
int j=trip[2]-1;
nums[i]+=val;
if(j+1<max){
nums[j+1]-=val;
}
}
//各个
int res[]=new int[max];
res[0]=nums[0];
for(int i=1;i<max;i++){
res[i]=nums[i]+res[i-1];
if(res[i]>capacity) return false;
}
return true;
}
}
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