C++面试算法题

客官°小女子只卖身不卖艺 2022-10-11 01:18 106阅读 0赞

### 1、实现strcpy(字符串拷贝) ###

#include<iostream>
    #include<stdio.h>
    using namespace std;
    char* myStrcpy(char* destination, const char * source)
    { 
    	if (!source)
    		return nullptr;
    	int i = 0;
    	while (source[i] != '\0'){ 
    		destination[i] = source[i];
    		++i;
    	}
    	return destination;
    }
    
    int main()
    { 
    	char source[32] = {  'h', 'e', 'l', 'l', 'o' ,'\0'};
    	char des[32] = { };
    	myStrcpy(des, source);
    	cout << des << endl;
    	
    	system("pause");
    	return 0;
    }

### 2、实现strcat(字符串连接) ###

#include<iostream>
    #include<stdio.h>
    using namespace std;
    char* myStrcat(char* destination, const char * source)
    { 
    	if (!source)
    		return destination;
    	int i = 0;
    	int j = 0;
    	while (destination[i] != '\0'){ 
    		++i;
    	}
    	while (source[j] != '\0')
    	{ 
    		destination[i] = source[j];
    		++i;
    		++j;
    	}
    	destination[i] = '\0';
    	return destination;
    }
    
    int main()
    { 
    	char source[32] = {  'w', 'o', 'r', 'l', 'd' };
    	char des[32] = {  'h', 'e', 'l', 'l', 'o', '\0' };
    	cout << myStrcat(des, source) << endl;
    	system("pause");
    	return 0;
    }

### 3、实现字符串逆序 ###

#include<iostream>
    #include<stdio.h>
    using namespace std;
    char* myStrReverse(char * source)
    { 
    	int begin = 0, end = strlen(source)-1;
    	char temp;
    	while (begin < end){ 
    		temp = source[begin];
    		source[begin] = source[end];
    		source[end] = temp;
    		++begin;
    		--end;
    	}
    	return source;
    }
    
    int main()
    { 
    	char source[32] = {  'w', 'o', 'r', 'l', 'd',' ','h', 'e', 'l', 'l', 'o', '\0' };
    	cout << myStrReverse(source) << endl;
    	system("pause");
    	return 0;
    }

### 4、C语言中字符串转数字的方法是什么( atoi )，请实现它 ###

#include "stdafx.h"
    #include<iostream>
    #include<stdio.h>
    using namespace std;
    int myAtoi(char* source)
    { 
    	if (!source)
    		return 0;
    	int i = strlen(source) -1;
    	int num = 0;
    	while (i >= 0)
    	{ 
    		num = num * 10 + source[i]-'0';
    		--i;
    	}
    	return num;
    }
    
    int main()
    { 
    	char source[32] = {  '1','2','3','4','\0' };
    	cout << myAtoi(source) << endl;
    	system("pause");
    	return 0;
    }

### 5、实现一个将字符串中所有字母转换为大写的方法 ###

char* myTran(char* source)
    { 
    	if (!source)
    		return 0;
    	int i = strlen(source) -1;
    	while (i >= 0)
    	{ 
    		source[i] = source[i] - ' ';
    		--i;
    	}
    	return source;
    }
    
    int main()
    { 
    	char source[32] = {  'h','e','l','l','\0' };
    	cout << myTran(source) << endl;
    	system("pause");
    	return 0;
    }

### 6、判断X年X月X日是这年的第几天 ###

int howDay(int year,int month,int day)
    { 
    	int chart[13] = {  0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
    	if (year % 4 == 0){ 
    		++chart[2];
    	}
    	int days = day;
    	month -= 1;
    	while (month > 0){ 
    		days += chart[month];
    		--month;
    	}
    	
    	return days;
    }
    
    int main()
    { 
    	cout << howDay(2024,3,3) << endl;
    	system("pause");
    	return 0;
    }

### 7、删除链表中值为Value的所有元素( \[Head\]->\[node1\]->\[node2\]->…\[noden\] ) ###

不想写

### 8、实现strncpy ###

char* myStrncpy(char* dest, const char* src, size_t n){ 
    	for (int i = 0; i < n; i++){ 
    		if (src[i] != '\0'){ 
    			dest[i] = src[i];
    		}
    		else{ 
    			while (i < n){ 
    				dest[i] = ' ';
    				i++;
    			}
    			return dest;
    		}	
    	}
    	return dest;
    }
    
    int main()
    { 
    	char dest[10] = { };
    	char src[10] = {  'n', 'i', 'h', 'a', 'o' ,'\0'};
    	cout << myStrncpy(dest, src, 8) <<"lllll" <<endl;
    	system("pause");
    	return 0;
    }

### 9、在母字符串中查找子字符串出现的次数 ###

不想写

### 10、给定一个字符串，按单词将该字符串逆序，比如给定"This is a sentence"，则输出是"sentence a is This"，为了简化问题，字符串中不包含标点符号 ###

不想写

### 11、在一个字符串中找到第一个只出现一次的字符。如输入abaccdeff，则输出b ###

char findFirst(const char* src){ 
    	int i = 0;
    	unordered_set<int> finded;
    	while (src[i] != '\0'){ 
    		if (finded.find(src[i]) != finded.end()){ 
    			++i;
    			continue;
    		}	
    		int j = i + 1;
    		while (src[j] != '\0'){ 
    			if (src[j] == src[i]){ 
    				finded.insert(src[j]);
    				break;
    			}
    			++j;
    		}
    		if (src[j] == '\0'){ 
    			return src[i];
    		}
    		++i;
    		
    	}
    	return ' ';
    }

### 12、写一个函数 ###

它的原形是`int continumax(char *outputstr,char *intputstr)`。  
功能：在字符串中找出连续最长的数字串，把这个串的长度返回，并把这个最长数字串付给其中一个函数参数outputstr所指内存。例如："abcd12345ed125ss123456789"的首地址传给intputstr后，函数将返回9，outputstr所指的值为123456789

int continumax(char* outputstr, char* intputstr){ 
    	int i = 0;
    	int resIndex = 0;
    	int resLength = 0;
    	int maxLength = 0;
    	//找出最长数字子串
    	while (intputstr[i] != '\0'){ 
    		if (intputstr[i] <= '9' && intputstr[i] >= '0'){ 
    			++maxLength;
    			if (maxLength > resLength){ 
    				resLength = maxLength;
    				resIndex = i - resLength +1;
    			}
    		}
    		else{ 
    			maxLength = 0;	
    		}
    		++i; 
    	}
    	for (int j = 0; j < resLength; j++){ 
    		outputstr[j] = intputstr[resIndex];
    		++resIndex;
    	}
    	outputstr[resLength] = '\0';
    	return resLength;
    }
    int main()
    { 
    	char outPut[32] = { };
    	cout << outPut << endl;
    	cout << continumax(outPut,"abcd12345ed125ss123456789") << endl;
    	cout << outPut << endl;
    	system("pause");
    	return 0;
    }