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Commit 9611896

Browse files
Merge branch 'youngyangyang04:master' into master
2 parents b8b62ff + 047c4db commit 9611896

16 files changed

+349
-52
lines changed

‎README.md‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -254,7 +254,7 @@
254254
33. [二叉树:构造一棵搜索树](./problems/0108.将有序数组转换为二叉搜索树.md)
255255
34. [二叉树:搜索树转成累加树](./problems/0538.把二叉搜索树转换为累加树.md)
256256
35. [二叉树:总结篇!(需要掌握的二叉树技能都在这里了)](./problems/二叉树总结篇.md)
257-
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258258
## 回溯算法
259259

260260
题目分类大纲如下:

‎problems/0035.搜索插入位置.md‎

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Original file line numberDiff line numberDiff line change
@@ -318,6 +318,31 @@ func searchInsert(_ nums: [Int], _ target: Int) -> Int {
318318
```
319319

320320

321+
### PHP
322+
323+
```php
324+
// 二分法(1):[左闭右闭]
325+
function searchInsert($nums, $target)
326+
{
327+
$n = count($nums);
328+
$l = 0;
329+
$r = $n - 1;
330+
while ($l <= $r) {
331+
$mid = floor(($l + $r) / 2);
332+
if ($nums[$mid] > $target) {
333+
// 下次搜索在左区间:[$l,$mid-1]
334+
$r = $mid - 1;
335+
} else if ($nums[$mid] < $target) {
336+
// 下次搜索在右区间:[$mid+1,$r]
337+
$l = $mid + 1;
338+
} else {
339+
// 命中返回
340+
return $mid;
341+
}
342+
}
343+
return $r + 1;
344+
}
345+
```
321346

322347

323348
-----------------------

‎problems/0039.组合总和.md‎

Lines changed: 2 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -370,18 +370,17 @@ func backtracking(startIndex,sum,target int,candidates,trcak []int,res *[][]int)
370370
```js
371371
var combinationSum = function(candidates, target) {
372372
const res = [], path = [];
373-
candidates.sort(); // 排序
373+
candidates.sort((a,b)=>a-b); // 排序
374374
backtracking(0, 0);
375375
return res;
376376
function backtracking(j, sum) {
377-
if (sum > target) return;
378377
if (sum === target) {
379378
res.push(Array.from(path));
380379
return;
381380
}
382381
for(let i = j; i < candidates.length; i++ ) {
383382
const n = candidates[i];
384-
if(n > target - sum) continue;
383+
if(n > target - sum) break;
385384
path.push(n);
386385
sum += n;
387386
backtracking(i, sum);

‎problems/0040.组合总和II.md‎

Lines changed: 10 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -508,22 +508,27 @@ func backtracking(startIndex,sum,target int,candidates,trcak []int,res *[][]int)
508508
*/
509509
var combinationSum2 = function(candidates, target) {
510510
const res = []; path = [], len = candidates.length;
511-
candidates.sort();
511+
candidates.sort((a,b)=>a-b);
512512
backtracking(0, 0);
513513
return res;
514514
function backtracking(sum, i) {
515-
if (sum > target) return;
516515
if (sum === target) {
517516
res.push(Array.from(path));
518517
return;
519518
}
520-
let f = -1;
521519
for(let j = i; j < len; j++) {
522520
const n = candidates[j];
523-
if(n > target - sum || n === f) continue;
521+
if(j > i && candidates[j] === candidates[j-1]){
522+
//若当前元素和前一个元素相等
523+
//则本次循环结束,防止出现重复组合
524+
continue;
525+
}
526+
//如果当前元素值大于目标值-总和的值
527+
//由于数组已排序,那么该元素之后的元素必定不满足条件
528+
//直接终止当前层的递归
529+
if(n > target - sum) break;
524530
path.push(n);
525531
sum += n;
526-
f = n;
527532
backtracking(sum, j + 1);
528533
path.pop();
529534
sum -= n;

‎problems/0070.爬楼梯.md‎

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Original file line numberDiff line numberDiff line change
@@ -308,7 +308,58 @@ var climbStairs = function(n) {
308308
};
309309
```
310310

311+
TypeScript
312+
313+
> 爬2阶
314+
315+
```typescript
316+
function climbStairs(n: number): number {
317+
/**
318+
dp[i]: i阶楼梯的方法种数
319+
dp[1]: 1;
320+
dp[2]: 2;
321+
...
322+
dp[i]: dp[i - 1] + dp[i - 2];
323+
*/
324+
const dp: number[] = [];
325+
dp[1] = 1;
326+
dp[2] = 2;
327+
for (let i = 3; i <= n; i++) {
328+
dp[i] = dp[i - 1] + dp[i - 2];
329+
}
330+
return dp[n];
331+
};
332+
```
333+
334+
> 爬m阶
335+
336+
```typescript
337+
function climbStairs(n: number): number {
338+
/**
339+
一次可以爬m阶
340+
dp[i]: i阶楼梯的方法种数
341+
dp[1]: 1;
342+
dp[2]: 2;
343+
dp[3]: dp[2] + dp[1];
344+
...
345+
dp[i]: dp[i - 1] + dp[i - 2] + ... + dp[max(i - m, 1)]; 从i-1加到max(i-m, 1)
346+
*/
347+
const m: number = 2; // 本题m为2
348+
const dp: number[] = new Array(n + 1).fill(0);
349+
dp[1] = 1;
350+
dp[2] = 2;
351+
for (let i = 3; i <= n; i++) {
352+
const end: number = Math.max(i - m, 1);
353+
for (let j = i - 1; j >= end; j--) {
354+
dp[i] += dp[j];
355+
}
356+
}
357+
return dp[n];
358+
};
359+
```
360+
311361
### C
362+
312363
```c
313364
int climbStairs(int n){
314365
//若n<=2,返回n

‎problems/0300.最长上升子序列.md‎

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Original file line numberDiff line numberDiff line change
@@ -168,6 +168,39 @@ func lengthOfLIS(nums []int ) int {
168168
}
169169
```
170170

171+
```go
172+
// 动态规划求解
173+
func lengthOfLIS(nums []int) int {
174+
// dp数组的定义 dp[i]表示取第i个元素的时候,表示子序列的长度,其中包括 nums[i] 这个元素
175+
dp := make([]int, len(nums))
176+
177+
// 初始化,所有的元素都应该初始化为1
178+
for i := range dp {
179+
dp[i] = 1
180+
}
181+
182+
ans := dp[0]
183+
for i := 1; i < len(nums); i++ {
184+
for j := 0; j < i; j++ {
185+
if nums[i] > nums[j] {
186+
dp[i] = max(dp[i], dp[j] + 1)
187+
}
188+
}
189+
if dp[i] > ans {
190+
ans = dp[i]
191+
}
192+
}
193+
return ans
194+
}
195+
196+
func max(x, y int) int {
197+
if x > y {
198+
return x
199+
}
200+
return y
201+
}
202+
```
203+
171204
Javascript
172205
```javascript
173206
const lengthOfLIS = (nums) => {

‎problems/0383.赎金信.md‎

Lines changed: 15 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -114,23 +114,25 @@ Java:
114114
```Java
115115
class Solution {
116116
public boolean canConstruct(String ransomNote, String magazine) {
117-
//记录杂志字符串出现的次数
118-
int[] arr = new int[26];
119-
int temp;
120-
for (int i = 0; i < magazine.length(); i++) {
121-
temp = magazine.charAt(i) - 'a';
122-
arr[temp]++;
117+
// 定义一个哈希映射数组
118+
int[] record = new int[26];
119+
120+
// 遍历
121+
for(char c : magazine.toCharArray()){
122+
record[c - 'a'] += 1;
123+
}
124+
125+
for(char c : ransomNote.toCharArray()){
126+
record[c - 'a'] -= 1;
123127
}
124-
for (int i = 0; i < ransomNote.length(); i++) {
125-
temp = ransomNote.charAt(i) - 'a';
126-
//对于金信中的每一个字符都在数组中查找
127-
//找到相应位减一,否则找不到返回false
128-
if (arr[temp] > 0) {
129-
arr[temp]--;
130-
} else {
128+
129+
// 如果数组中存在负数,说明ransomNote字符串总存在magazine中没有的字符
130+
for(int i : record){
131+
if(i < 0){
131132
return false;
132133
}
133134
}
135+
134136
return true;
135137
}
136138
}

‎problems/0496.下一个更大元素I.md‎

Lines changed: 33 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -244,6 +244,39 @@ class Solution:
244244
```
245245

246246
Go:
247+
248+
> 未精简版本
249+
```go
250+
func nextGreaterElement(nums1 []int, nums2 []int) []int {
251+
res := make([]int, len(nums1))
252+
for i := range res { res[i] = -1 }
253+
m := make(map[int]int, len(nums1))
254+
for k, v := range nums1 { m[v] = k }
255+
256+
stack := []int{0}
257+
for i := 1; i < len(nums2); i++ {
258+
top := stack[len(stack)-1]
259+
if nums2[i] < nums2[top] {
260+
stack = append(stack, i)
261+
} else if nums2[i] == nums2[top] {
262+
stack = append(stack, i)
263+
} else {
264+
for len(stack) != 0 && nums2[i] > nums2[top] {
265+
if v, ok := m[nums2[top]]; ok {
266+
res[v] = nums2[i]
267+
}
268+
stack = stack[:len(stack)-1]
269+
if len(stack) != 0 {
270+
top = stack[len(stack)-1]
271+
}
272+
}
273+
stack = append(stack, i)
274+
}
275+
}
276+
return res
277+
}
278+
```
279+
> 精简版本
247280
```go
248281
func nextGreaterElement(nums1 []int, nums2 []int) []int {
249282
res := make([]int, len(nums1))

‎problems/0509.斐波那契数.md‎

Lines changed: 22 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -245,7 +245,29 @@ var fib = function(n) {
245245
};
246246
```
247247

248+
TypeScript
249+
250+
```typescript
251+
function fib(n: number): number {
252+
/**
253+
dp[i]: 第i个斐波那契数
254+
dp[0]: 0;
255+
dp[1]:1;
256+
...
257+
dp[i] = dp[i - 1] + dp[i - 2];
258+
*/
259+
const dp: number[] = [];
260+
dp[0] = 0;
261+
dp[1] = 1;
262+
for (let i = 2; i <= n; i++) {
263+
dp[i] = dp[i - 1] + dp[i - 2];
264+
}
265+
return dp[n];
266+
};
267+
```
268+
248269
### C
270+
249271
动态规划:
250272
```c
251273
int fib(int n){

‎problems/0674.最长连续递增序列.md‎

Lines changed: 39 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -236,6 +236,45 @@ class Solution:
236236
```
237237

238238
Go:
239+
> 动态规划:
240+
```go
241+
func findLengthOfLCIS(nums []int) int {
242+
if len(nums) == 0 {return 0}
243+
res, count := 1, 1
244+
for i := 0; i < len(nums)-1; i++ {
245+
if nums[i+1] > nums[i] {
246+
count++
247+
}else {
248+
count = 1
249+
}
250+
if count > res {
251+
res = count
252+
}
253+
}
254+
return res
255+
}
256+
```
257+
258+
> 贪心算法:
259+
```go
260+
func findLengthOfLCIS(nums []int) int {
261+
if len(nums) == 0 {return 0}
262+
dp := make([]int, len(nums))
263+
for i := 0; i < len(dp); i++ {
264+
dp[i] = 1
265+
}
266+
res := 1
267+
for i := 0; i < len(nums)-1; i++ {
268+
if nums[i+1] > nums[i] {
269+
dp[i+1] = dp[i] + 1
270+
}
271+
if dp[i+1] > res {
272+
res = dp[i+1]
273+
}
274+
}
275+
return res
276+
}
277+
```
239278

240279
Javascript:
241280

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