剑指offer第三十题：最小的k个数
1 //============================================================================
2 // Name : JZ-C-30.cpp
3 // Author : Laughing_Lz
4 // Version :
5 // Copyright : All Right Reserved
6 // Description : 最小的k个数
7 //============================================================================
8
9 #include <iostream>
10 #include <stdio.h>
11 #include <set>
12 #include <vector>
13 #include "Array.h"
14 using namespace std;
15
16 using namespace std;
17
18 // ====================方法1:同样可利用分治法====================
19 void GetLeastNumbers_Solution1(int* input, int n, int* output, int k)
20 {
21 if(input == NULL || output == NULL || k > n || n <= 0 || k <= 0)
22 return;
23
24 int start = 0;
25 int end = n - 1;
26 int index = Partition(input, n, start, end);
27 while(index != k - 1)
28 {
29 if(index > k - 1)
30 {
31 end = index - 1;
32 index = Partition(input, n, start, end);
33 }
34 else
35 {
36 start = index + 1;
37 index = Partition(input, n, start, end);
38 }
39 }
40
41 for(int i = 0; i < k; ++i)
42 output[i] = input[i];//查找后，放入output数组
43 }
44
45 // ====================方法2:堆、红黑树：set、multiset都是基于红黑树实现的====================
46 typedef multiset<int, greater<int> > intSet;
47 typedef multiset<int, greater<int> >::iterator setIterator;
48
49 void GetLeastNumbers_Solution2(const vector<int>& data, intSet& leastNumbers, int k)
50 {
51 leastNumbers.clear();
52
53 if(k < 1 || data.size() < k)
54 return;
55
56 vector<int>::const_iterator iter = data.begin();
57 for(; iter != data.end(); ++ iter)
58 {
59 if((leastNumbers.size()) < k)
60 leastNumbers.insert(*iter);
61
62 else
63 {
64 setIterator iterGreatest = leastNumbers.begin();
65
66 if(*iter < *(leastNumbers.begin()))
67 {
68 leastNumbers.erase(iterGreatest);
69 leastNumbers.insert(*iter);
70 }
71 }
72 }
73 }
74
75 // ====================测试代码====================
76 void Test(char* testName, int* data, int n, int* expectedResult, int k)
77 {
78 if(testName != NULL)
79 printf("%s begins: \n", testName);
80
81 vector<int> vectorData;
82 for(int i = 0; i < n; ++ i)
83 vectorData.push_back(data[i]);
84
85 if(expectedResult == NULL)
86 printf("The input is invalid, we don‘t expect any result.\n");
87 else
88 {
89 printf("Expected result: \n");
90 for(int i = 0; i < k; ++ i)
91 printf("%d\t", expectedResult[i]);
92 printf("\n");
93 }
94
95 printf("Result for solution1:\n");
96 int* output = new int[k];
97 GetLeastNumbers_Solution1(data, n, output, k);
98 if(expectedResult != NULL)
99 {
100 for(int i = 0; i < k; ++ i)
101 printf("%d\t", output[i]);
102 printf("\n");
103 }
104
105 delete[] output;
106
107 printf("Result for solution2:\n");
108 intSet leastNumbers;
109 GetLeastNumbers_Solution2(vectorData, leastNumbers, k);
110 printf("The actual output numbers are:\n");
111 for(setIterator iter = leastNumbers.begin(); iter != leastNumbers.end(); ++iter)
112 printf("%d\t", *iter);
113 printf("\n\n");
114 }
115
116 // k小于数组的长度
117 void Test1()
118 {
119 int data[] = {4, 5, 1, 6, 2, 7, 3, 8};
120 int expected[] = {1, 2, 3, 4};
121 Test("Test1", data, sizeof(data) / sizeof(int), expected, sizeof(expected) / sizeof(int));
122 }
123
124 // k等于数组的长度
125 void Test2()
126 {
127 int data[] = {4, 5, 1, 6, 2, 7, 3, 8};
128 int expected[] = {1, 2, 3, 4, 5, 6, 7, 8};
129 Test("Test2", data, sizeof(data) / sizeof(int), expected, sizeof(expected) / sizeof(int));
130 }
131
132 // k大于数组的长度
133 void Test3()
134 {
135 int data[] = {4, 5, 1, 6, 2, 7, 3, 8};
136 int* expected = NULL;
137 Test("Test3", data, sizeof(data) / sizeof(int), expected, 10);
138 }
139
140 // k等于1
141 void Test4()
142 {
143 int data[] = {4, 5, 1, 6, 2, 7, 3, 8};
144 int expected[] = {1};
145 Test("Test4", data, sizeof(data) / sizeof(int), expected, sizeof(expected) / sizeof(int));
146 }
147
148 // k等于0
149 void Test5()
150 {
151 int data[] = {4, 5, 1, 6, 2, 7, 3, 8};
152 int* expected = NULL;
153 Test("Test5", data, sizeof(data) / sizeof(int), expected, 0);
154 }
155
156 // 数组中有相同的数字
157 void Test6()
158 {
159 int data[] = {4, 5, 1, 6, 2, 7, 2, 8};
160 int expected[] = {1, 2};
161 Test("Test6", data, sizeof(data) / sizeof(int), expected, sizeof(expected) / sizeof(int));
162 }
163
164 // 输入空指针
165 void Test7()
166 {
167 int* expected = NULL;
168 Test("Test7", NULL, NULL, expected, 0);
169 }
170
171 int main(int argc, char** argv)
172 {
173 Test1();
174 Test2();
175 Test3();
176 Test4();
177 Test5();
178 Test6();
179 Test7();
180
181 return 0;
182 }
关于Partition方法：
1 // 《剑指Offer——名企面试官精讲典型编程题》代码
2 // 著作权所有者：何海涛
3
4 #include <stdlib.h>
5 #include <stdio.h>
6 #include "Array.h"
7 #include <exception>
8
9 // Random Partition
10 int RandomInRange(int min, int max) {
11 int random = rand() % (max - min + 1) + min;
12 return random;
13 }
14
15 void Swap(int* num1, int* num2) {
16 int temp = *num1;
17 *num1 = *num2;
18 *num2 = temp;
19 }
20
21 int Partition(int data[], int length, int start, int end) {
22 if (data == NULL || length <= 0 || start < 0 || end >= length) {
23 printf("Invalid Parameters");
24 throw new std::exception();//这里括号里为什么不能加msg？？？！！！
25 }
26 int index = RandomInRange(start, end);
27 Swap(&data[index], &data[end]);
28
29 int small = start - 1;
30 for (index = start; index < end; ++index) {
31 if (data[index] < data[end]) {
32 ++small;
33 if (small != index)
34 Swap(&data[index], &data[small]);
35 }
36 }
37
38 ++small;
39 Swap(&data[small], &data[end]);
40
41 return small;
42 }
时间： 2024-07-30 19:59:05