for (int j = 0; j < 10; j++) {
result *= a[i][j];
}
}
int count = 0;
while (result % 10 == 0) {
count++;
result /= 10;
}
printf("The number of zeros at the end of the product is %d.\n", count);
return 0;
}
粗看原理好像是对的，先全部相乘再循环计数。可惜实现不了，所有整数相乘肯定会溢出了。
#### 5. 四数之和
给定一个包含 n 个整数的数组 nums 和一个目标值 target，判断 nums 中是否存在四个元素 a，b，c 和 d ，使得 a + b + c + d 的值与 target 相等？找出所有满足条件且不重复的四元组，用python代码实现。
def fourSum(nums, target): res = [] nums.sort() for i in range(len(nums)-3): if i > 0 and nums[i] == nums[i-1]: continue for j in range(i+1, len(nums)-2): if j > i+1 and nums[j] == nums[j-1]: continue l, r = j+1, len(nums)-1 while l < r: s = nums[i] + nums[j] + nums[l] + nums[r] if s == target: res.append([nums[i], nums[j], nums[l], nums[r]]) while l < r and nums[l] == nums[l+1]: l += 1 while l < r and nums[r] == nums[r-1]: r -= 1 l += 1 r -= 1 elif s < target: l += 1 else: r -= 1 return res
#### 6. 字符串编码
问题描述
小明发明了一种给由全大写字母组成的字符串编码的方法。
对于每一个大写字母，小明将它转换成它在 26 个英文字母中序号，即 A → 1, B → 2, … Z →26。
这样一个字符串就能被转化成一个数字序列：比如 ABCXYZ → 123242526。
现在给定一个转换后的数字序列，小明想还原出原本的字符串。
当然这样的还原有可能存在多个符合条件的字符串。
小明希望找出其中字典序最大的字符串。
请用C++代码来实现：
输入格式
一个数字序列。
输出格式
一个只包含大写字母的字符串，代表答案
样例输入
123242526
样例输出
LCXYZ
#include #include #include using namespace std; int main() { string s; cin >> s; string ans = ""; for (int i = 0; i < s.length(); i++) { int num = s[i] - '0'; char c = 'A' + num - 1; ans += c; } sort(ans.begin(), ans.end(), greater()); cout << ans << endl; return 0; }
测试错误，输入123242526 输出 FEDCBBBBA。你能找出错在哪里吗？
写一段正确的参考代码，如下：
#include <bits/stdc++.h> using namespace std;
int main() { string in; string re = ""; cin >> in; int len = in.length();
in = in + 'Z';
for (int i = 0; i < len;)
{
int temp = int(in[i] - '0') * 10 + int(in[i + 1] - '0');
if (temp > 26)
{
re = re + char(in[i] - '0' + 'A' - 1);
i++;
}
else
{
re = re+char(temp + 'A' - 1);
i += 2;
}
}
cout << re;
return 0;
}
#### 7. 请给出七大排序算法的python代码。
#1. 冒泡排序： def bubble_sort(nums): for i in range(len(nums)-1): for j in range(len(nums)-i-1): if nums[j] > nums[j+1]: nums[j], nums[j+1] = nums[j+1], nums[j] return nums
#2. 选择排序： def selection_sort(nums): for i in range(len(nums)-1): min_index = i for j in range(i+1, len(nums)): if nums[j] < nums[min_index]: min_index = j nums[i], nums[min_index] = nums[min_index], nums[i] return nums
#3. 插入排序： def insertion_sort(nums): for i in range(1, len(nums)): j = i while j > 0 and nums[j] < nums[j-1]: nums[j], nums[j-1] = nums[j-1], nums[j] j -= 1 return nums
#4. 希尔排序： def shell_sort(nums): gap = len(nums) // 2 while gap > 0: for i in range(gap, len(nums)): j = i while j >= gap and nums[j] < nums[j-gap]: nums[j], nums[j-gap] = nums[j-gap], nums[j] j -= gap gap //= 2 return nums
#5. 归并排序： def merge_sort(nums): if len(nums) <= 1: return nums mid = len(nums) // 2 left = merge_sort(nums[:mid]) right = merge_sort(nums[mid:]) return merge(left, right) def merge(left, right): res = [] while left and right: if left[0] <= right[0]: res.append(left.pop(0)) else: res.append(right.pop(0)) res += left res += right return res
#6. 快速排序： def quick_sort(nums): if len(nums) <= 1: return nums pivot = nums[0] left = [x for x in nums[1:] if x < pivot] right = [x for x in nums[1:] if x >= pivot] return quick_sort(left) + [pivot] + quick_sort(right)
#7. 堆排序： def heap_sort(nums): n = len(nums) for i in range(n//2-1, -1, -1): heapify(nums, n, i) for i in range(n-1, 0, -1): nums[i], nums[0] = nums[0], nums[i] heapify(nums, i, 0) return nums def heapify(nums, n, i): largest = i l = 2i + 1 r = 2i + 2 if l < n and nums[i] < nums[l]: largest = l if r < n and nums[largest] < nums[r]: largest = r if largest != i: nums[i], nums[largest] = nums[largest], nums[i] heapify(nums, n, largest)
#### 8. 请给出七大排序算法的C代码。
1.冒泡排序： void bubble_sort(int arr[], int n) { int i, j; for (i = 0; i < n-1; i++)
for (j = 0; j < n-i-1; j++)
if (arr[j] > arr[j+1])
swap(&arr[j], &arr[j+1]);
}
//2.选择排序： void selection_sort(int arr[], int n) { int i, j, min_idx;
for (i = 0; i < n-1; i++)
{
min_idx = i;
for (j = i+1; j < n; j++)
if (arr[j] < arr[min_idx])
min_idx = j;
swap(&arr[min_idx], &arr[i]);
}
}
//3.插入排序： void insertion_sort(int arr[], int n) { int i, key, j; for (i = 1; i < n; i++) { key = arr[i]; j = i-1;
while (j >= 0 && arr[j] > key)
{
arr[j+1] = arr[j];
j = j-1;
}
arr[j+1] = key;
} }
//4.希尔排序：
void shell_sort(int arr[], int n)
{
for (int gap = n/2; gap > 0; gap /= 2)
{
for (int i = gap; i < n; i += 1)
{
int temp = arr[i];
int j;
for (j = i; j >= gap && arr[j - gap] > temp; j -= gap)
arr[j] = arr[j - gap];
arr[j] = temp;
}
}
}
//5.归并排序： void merge(int arr[], int l, int m, int r) { int i, j, k; int n1 = m - l + 1; int n2 = r - m;
int L[n1], R[n2];
for (i = 0; i < n1; i++)
L[i] = arr[l + i];
for (j = 0; j < n2; j++)
R[j] = arr[m + 1+ j];
i = 0;
j = 0;
k = l;
while (i < n1 && j < n2)
{
if (L[i] <= R[j])
{
arr[k] = L[i];
i++;
}
else
{
arr[k] = R[j];
j++;
}
k++;
}
while (i < n1)
{
arr[k] = L[i];
i++;
k++;
}
while (j < n2)
{
arr[k] = R[j];
j++;
k++;
}
} void merge_sort(int arr[], int l, int r) { if (l < r) { int m = l+(r-l)/2; merge_sort(arr, l, m); merge_sort(arr, m+1, r);
merge(arr, l, m, r);
}
}
//6.快速排序：
int partition (int arr[], int low, int high)
{
int pivot = arr[high];
int i = (low - 1);
for (int j = low; j <= high- 1; j++)
{
if (arr[j] <= pivot)
{
i++;
swap(&arr[i], &arr[j]);
}
}
swap(&arr[i + 1], &arr[high]);
return (i + 1);
} void quick_sort(int arr[], int low, int high) { if (low < high) { int pi = partition(arr, low, high); quick_sort(arr, low, pi - 1); quick_sort(arr, pi + 1, high); } }
//7.堆排序： void heapify(int arr[], int n, int i) { int largest = i; int l = 2i + 1; int r = 2i + 2;
if (l < n && arr[l] > arr[largest])
largest = l;
if (r < n && arr[r] > arr[largest])
largest = r;
if (largest != i)
{
swap(arr[i], arr[largest]);
heapify(arr, n, largest);
}
} void heap_sort(int arr[], int n) { for (int i = n / 2 - 1; i >= 0; i--) heapify(arr, n, i);
for (int i=n-1; i>=0; i--)
{
swap(arr[0], arr[i]);
heapify(arr, i, 0);
}
}
#### 9. 请给出七大排序算法的Java代码。
//1. 冒泡排序： public static void bubbleSort(int[] arr) { int n = arr.length; for (int i = 0; i < n - 1; i++) { for (int j = 0; j < n - i - 1; j++) { if (arr[j] > arr[j + 1]) { int temp = arr[j]; arr[j] = arr[j + 1]; arr[j + 1] = temp; } } } }
//2. 选择排序： public static void selectionSort(int[] arr) { int n = arr.length; for (int i = 0; i < n - 1; i++) { int minIndex = i; for (int j = i + 1; j < n; j++) { if (arr[j] < arr[minIndex]) { minIndex = j; } } int temp = arr[i]; arr[i] = arr[minIndex]; arr[minIndex] = temp; } }
//3. 插入排序： public static void insertionSort(int[] arr) { int n = arr.length; for (int i = 1; i < n; i++) { int value = arr[i]; int j = i - 1; while (j >= 0 && arr[j] > value) { arr[j + 1] = arr[j]; j--; } arr[j + 1] = value; } }
//4. 希尔排序： public static void shellSort(int[] arr) { int n = arr.length; for (int gap = n / 2; gap > 0; gap /= 2) { for (int i = gap; i < n; i++) { int value = arr[i]; int j = i - gap; while (j >= 0 && arr[j] > value) { arr[j + gap] = arr[j]; j -= gap; } arr[j + gap] = value; } } }
//5. 归并排序： public static void mergeSort(int[] arr) { int n = arr.length; if (n < 2) { return; } int mid = n / 2; int[] left = new int[mid]; int[] right = new int[n - mid]; for (int i = 0; i < mid; i++) { left[i] = arr[i]; } for (int i = mid; i < n; i++) { right[i - mid] = arr[i]; } mergeSort(left); mergeSort(right); merge(arr, left, right); } public static void merge(int[] arr, int[] left, int[] right) { int i = 0, j = 0, k = 0; int leftLen = left.length; int rightLen = right.length; while (i < leftLen && j < rightLen) { if (left[i] <= right[j]) { arr[k++] = left[i++]; } else { arr[k++] = right[j++]; } } while (i < leftLen) { arr[k++] = left[i++]; } while (j < rightLen) { arr[k++] = right[j++]; } }
//6. 快速排序： public static void quickSort(int[] arr, int low, int high) { if (low < high) { int pivot = partition(arr, low, high); quickSort(arr, low, pivot - 1); quickSort(arr, pivot + 1, high); } } public static int partition(int[] arr, int low, int high) { int pivot = arr[high]; int i = low - 1; for (int j = low; j < high; j++) { if (arr[j] <= pivot) { i++; int temp = arr[i]; arr[i] = arr[j]; arr[j] = temp; } } int temp = arr[i + 1]; arr[i + 1] = arr[high]; arr[high] = temp; return i + 1; }
//7. 堆排序： public static void heapSort(int[] arr) { int n = arr.length; for (int i = n / 2 - 1; i >= 0; i--) { heapify(arr, n, i); } for (int i = n - 1; i >= 0; i--) { int temp = arr[0]; arr[0] = arr[i]; arr[i] = temp; heapify(arr, i, 0); } } public static void heapify(int[] arr, int n, int i) { int largest = i; int left = 2 * i + 1; int right = 2 * i + 2; if (left < n && arr[left] > arr[largest]) { largest = left; } if (right < n && arr[right] > arr[largest]) { largest = right; } if (largest != i) { int temp = arr[i]; arr[i] = arr[largest]; arr[largest] = temp; heapify(arr, n, largest); } }
#### 10. 请给出十大排序算法的Golang代码。
//1. 冒泡排序： func BubbleSort(arr []int) { for i := 0; i < len(arr); i++ { for j := 0; j < len(arr)-i-1; j++ { if arr[j] > arr[j+1] { arr[j], arr[j+1] = arr[j+1], arr[j] } } } }
//2. 选择排序： func SelectionSort(arr []int) { for i := 0; i < len(arr); i++ { minIndex := i for j := i + 1; j < len(arr); j++ { if arr[j] < arr[minIndex] { minIndex = j } } arr[i], arr[minIndex] = arr[minIndex], arr[i] } }
//3. 插入排序： func InsertionSort(arr []int) { for i := 1; i < len(arr); i++ { for j := i; j > 0; j-- { if arr[j] < arr[j-1] { arr[j], arr[j-1] = arr[j-1], arr[j] } } } }
//4. 希尔排序： func ShellSort(arr []int) { n := len(arr) h := 1 for h < n/3 { h = 3*h + 1 } for h >= 1 { for i := h; i < n; i++ { for j := i; j >= h && arr[j] < arr[j-h]; j -= h { arr[j], arr[j-h] = arr[j-h], arr[j] } } h /= 3 } }
//5. 归并排序： func MergeSort(arr []int) { if len(arr) <= 1 { return } mid := len(arr) / 2 left := arr[:mid] right := arr[mid:] MergeSort(left) MergeSort(right) i := 0 j := 0 k := 0 for i < len(left) && j < len(right) { if left[i] < right[j] { arr[k] = left[i] i++ } else { arr[k] = right[j] j++ } k++ } for i < len(left) { arr[k] = left[i] i++ k++ } for j < len(right) { arr[k] = right[j] j++ k++ } }
//6. 快速排序： func QuickSort(arr []int) { if len(arr) <= 1 { return }
网上学习资料一大堆，但如果学到的知识不成体系，遇到问题时只是浅尝辄止，不再深入研究，那么很难做到真正的技术提升。
了解详情》docs.qq.com/doc/DSlVlZExWQ0FRSE9H
