Skip to content

Commit fd093f8

Browse files
yanglbmeyanglbme
committed
feat: add solutions to lc problem: No.0074
No.0074.Search a 2D Matrix
1 parent 39a782c commit fd093f8

File tree

3 files changed

+236
-20
lines changed

3 files changed

+236
-20
lines changed

‎solution/0000-0099/0074.Search a 2D Matrix/README.md

Lines changed: 134 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -44,14 +44,32 @@
4444

4545
<!-- 这里可写通用的实现逻辑 -->
4646

47+
**方法一：二分查找**
48+
4749
将二维矩阵逻辑展开，然后二分查找即可。
4850

51+
时间复杂度 O(logmn)。
52+
53+
**方法二：从左下角或右上角搜索**
54+
55+
这里我们以左下角作为起始搜索点，往右上方向开始搜索，比较当前元素 `matrix[i][j]`与 target 的大小关系：
56+
57+
- 若 `matrix[i][j] == target`，说明找到了目标值，直接返回 true。
58+
- 若 `matrix[i][j] > target`，说明这一行从当前位置开始往右的所有元素均大于 target，应该让 i 指针往上移动，即 `i--`。
59+
- 若 `matrix[i][j] < target`，说明这一列从当前位置开始往上的所有元素均小于 target，应该让 j 指针往右移动，即 `j++`。
60+
61+
若搜索结束依然找不到 target，返回 false。
62+
63+
时间复杂度 O(m + n)。
64+
4965
<!-- tabs:start -->
5066

5167
### **Python3**
5268

5369
<!-- 这里可写当前语言的特殊实现逻辑 -->
5470

71+
二分查找：
72+
5573
```python
5674
class Solution:
5775
def searchMatrix(self, matrix: List[List[int]], target: int) -> bool:
@@ -67,10 +85,29 @@ class Solution:
6785
return matrix[left // n][left % n] == target
6886
```
6987

88+
从左下角或右上角搜索：
89+
90+
```python
91+
class Solution:
92+
def searchMatrix(self, matrix: List[List[int]], target: int) -> bool:
93+
m, n = len(matrix), len(matrix[0])
94+
i, j = m - 1, 0
95+
while i >= 0 and j < n:
96+
if matrix[i][j] == target:
97+
return True
98+
if matrix[i][j] > target:
99+
i -= 1
100+
else:
101+
j += 1
102+
return False
103+
```
104+
70105
### **Java**
71106

72107
<!-- 这里可写当前语言的特殊实现逻辑 -->
73108

109+
二分查找：
110+
74111
```java
75112
class Solution {
76113
public boolean searchMatrix(int[][] matrix, int target) {
@@ -90,8 +127,31 @@ class Solution {
90127
}
91128
```
92129

130+
从左下角或右上角搜索：
131+
132+
```java
133+
class Solution {
134+
public boolean searchMatrix(int[][] matrix, int target) {
135+
int m = matrix.length, n = matrix[0].length;
136+
for (int i = m - 1, j = 0; i >= 0 && j < n;) {
137+
if (matrix[i][j] == target) {
138+
return true;
139+
}
140+
if (matrix[i][j] > target) {
141+
--i;
142+
} else {
143+
++j;
144+
}
145+
}
146+
return false;
147+
}
148+
}
149+
```
150+
93151
### **C++**
94152

153+
二分查找：
154+
95155
```cpp
96156
class Solution {
97157
public:
@@ -112,35 +172,82 @@ public:
112172
};
113173
```
114174
175+
从左下角或右上角搜索：
176+
177+
```cpp
178+
class Solution {
179+
public:
180+
bool searchMatrix(vector<vector<int>>& matrix, int target) {
181+
int m = matrix.size(), n = matrix[0].size();
182+
for (int i = m - 1, j = 0; i >= 0 && j < n;)
183+
{
184+
if (matrix[i][j] == target) return true;
185+
if (matrix[i][j] > target) --i;
186+
else ++j;
187+
}
188+
return false;
189+
}
190+
};
191+
```
192+
115193
### **JavaScript**
116194

195+
二分查找：
196+
117197
```js
118198
/**
119199
* @param {number[][]} matrix
120200
* @param {number} target
121201
* @return {boolean}
122202
*/
123203
var searchMatrix = function (matrix, target) {
124-
const m = matrix.length;
125-
const n = matrix[0].length;
126-
let left = 0;
127-
let right = m * n - 1;
204+
const m = matrix.length,
205+
n = matrix[0].length;
206+
let left = 0,
207+
right = m * n - 1;
128208
while (left < right) {
129-
const mid = (left + right) >> 1;
209+
const mid = (left + right + 1) >> 1;
130210
const x = Math.floor(mid / n);
131211
const y = mid % n;
132-
if (matrix[x][y] >= target) {
133-
right = mid;
212+
if (matrix[x][y] <= target) {
213+
left = mid;
134214
} else {
135-
left = mid + 1;
215+
right = mid - 1;
136216
}
137217
}
138218
return matrix[Math.floor(left / n)][left % n] == target;
139219
};
140220
```
141221

222+
从左下角或右上角搜索：
223+
224+
```js
225+
/**
226+
* @param {number[][]} matrix
227+
* @param {number} target
228+
* @return {boolean}
229+
*/
230+
var searchMatrix = function (matrix, target) {
231+
const m = matrix.length,
232+
n = matrix[0].length;
233+
for (let i = m - 1, j = 0; i >= 0 && j < n; ) {
234+
if (matrix[i][j] == target) {
235+
return true;
236+
}
237+
if (matrix[i][j] > target) {
238+
--i;
239+
} else {
240+
++j;
241+
}
242+
}
243+
return false;
244+
};
245+
```
246+
142247
### **Go**
143248

249+
二分查找：
250+
144251
```go
145252
func searchMatrix(matrix [][]int, target int) bool {
146253
m, n := len(matrix), len(matrix[0])
@@ -158,6 +265,25 @@ func searchMatrix(matrix [][]int, target int) bool {
158265
}
159266
```
160267

268+
从左下角或右上角搜索：
269+
270+
```go
271+
func searchMatrix(matrix [][]int, target int) bool {
272+
m, n := len(matrix), len(matrix[0])
273+
for i, j := m-1, 0; i >= 0 && j < n; {
274+
if matrix[i][j] == target {
275+
return true
276+
}
277+
if matrix[i][j] > target {
278+
i--
279+
} else {
280+
j++
281+
}
282+
}
283+
return false
284+
}
285+
```
286+
161287
### **...**
162288

163289
```

‎solution/0000-0099/0074.Search a 2D Matrix/README_EN.md

Lines changed: 98 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -57,6 +57,21 @@ class Solution:
5757
return matrix[left // n][left % n] == target
5858
```
5959

60+
```python
61+
class Solution:
62+
def searchMatrix(self, matrix: List[List[int]], target: int) -> bool:
63+
m, n = len(matrix), len(matrix[0])
64+
i, j = m - 1, 0
65+
while i >= 0 and j < n:
66+
if matrix[i][j] == target:
67+
return True
68+
if matrix[i][j] > target:
69+
i -= 1
70+
else:
71+
j += 1
72+
return False
73+
```
74+
6075
### **Java**
6176

6277
```java
@@ -78,6 +93,25 @@ class Solution {
7893
}
7994
```
8095

96+
```java
97+
class Solution {
98+
public boolean searchMatrix(int[][] matrix, int target) {
99+
int m = matrix.length, n = matrix[0].length;
100+
for (int i = m - 1, j = 0; i >= 0 && j < n;) {
101+
if (matrix[i][j] == target) {
102+
return true;
103+
}
104+
if (matrix[i][j] > target) {
105+
--i;
106+
} else {
107+
++j;
108+
}
109+
}
110+
return false;
111+
}
112+
}
113+
```
114+
81115
### **C++**
82116

83117
```cpp
@@ -100,6 +134,22 @@ public:
100134
};
101135
```
102136
137+
```cpp
138+
class Solution {
139+
public:
140+
bool searchMatrix(vector<vector<int>>& matrix, int target) {
141+
int m = matrix.size(), n = matrix[0].size();
142+
for (int i = m - 1, j = 0; i >= 0 && j < n;)
143+
{
144+
if (matrix[i][j] == target) return true;
145+
if (matrix[i][j] > target) --i;
146+
else ++j;
147+
}
148+
return false;
149+
}
150+
};
151+
```
152+
103153
### **JavaScript**
104154

105155
```js
@@ -109,24 +159,47 @@ public:
109159
* @return {boolean}
110160
*/
111161
var searchMatrix = function (matrix, target) {
112-
const m = matrix.length;
113-
const n = matrix[0].length;
114-
let left = 0;
115-
let right = m * n - 1;
162+
const m = matrix.length,
163+
n = matrix[0].length;
164+
let left = 0,
165+
right = m * n - 1;
116166
while (left < right) {
117-
const mid = (left + right) >> 1;
167+
const mid = (left + right + 1) >> 1;
118168
const x = Math.floor(mid / n);
119169
const y = mid % n;
120-
if (matrix[x][y] >= target) {
121-
right = mid;
170+
if (matrix[x][y] <= target) {
171+
left = mid;
122172
} else {
123-
left = mid + 1;
173+
right = mid - 1;
124174
}
125175
}
126176
return matrix[Math.floor(left / n)][left % n] == target;
127177
};
128178
```
129179

180+
```js
181+
/**
182+
* @param {number[][]} matrix
183+
* @param {number} target
184+
* @return {boolean}
185+
*/
186+
var searchMatrix = function (matrix, target) {
187+
const m = matrix.length,
188+
n = matrix[0].length;
189+
for (let i = m - 1, j = 0; i >= 0 && j < n; ) {
190+
if (matrix[i][j] == target) {
191+
return true;
192+
}
193+
if (matrix[i][j] > target) {
194+
--i;
195+
} else {
196+
++j;
197+
}
198+
}
199+
return false;
200+
};
201+
```
202+
130203
### **Go**
131204

132205
```go
@@ -146,6 +219,23 @@ func searchMatrix(matrix [][]int, target int) bool {
146219
}
147220
```
148221

222+
```go
223+
func searchMatrix(matrix [][]int, target int) bool {
224+
m, n := len(matrix), len(matrix[0])
225+
for i, j := m-1, 0; i >= 0 && j < n; {
226+
if matrix[i][j] == target {
227+
return true
228+
}
229+
if matrix[i][j] > target {
230+
i--
231+
} else {
232+
j++
233+
}
234+
}
235+
return false
236+
}
237+
```
238+
149239
### **...**
150240

151241
```

‎solution/0000-0099/0074.Search a 2D Matrix/Solution.js

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -4,10 +4,10 @@
44
* @return {boolean}
55
*/
66
var searchMatrix = function (matrix, target) {
7-
const m = matrix.length;
8-
const n = matrix[0].length;
9-
let left = 0;
10-
let right = m * n - 1;
7+
const m = matrix.length,
8+
n = matrix[0].length;
9+
let left = 0,
10+
right = m * n - 1;
1111
while (left < right) {
1212
const mid = (left + right + 1) >> 1;
1313
const x = Math.floor(mid / n);

0 commit comments

Comments
 (0)