算法笔记-----入门算法

3.1简单模拟

#include 
#include 
using namespace std;
int main()
{
	int n, step = 0;
	scanf("%d", &n);
	while (1) {
		if (n == 1) {
			break;
		}
		if (n % 2 == 0) {
			n /= 2;
		}
		else {
			n = (3 * n + 1) / 2;
		}
		++step;
	}
	printf("%d\n", step);
	system("pause");//vs里面防止控制台一闪而过。
	return 0;
}

#include 
#include 
using namespace std;
int main()
{
	int N,n,schoolcode,grade,maxschool=-1;
	int stu[100001] = {0};
	scanf("%d", &N);
	n = N;
	while (N--) {
		scanf("%d%d", &schoolcode, &grade);
		stu[schoolcode] += grade;
	}
	for (int i = 1; i <= n; ++i) {
		if (stu[i] > stu[maxschool]) {
			maxschool = i;
		}
	}
	printf("%d %d\n", maxschool, stu[maxschool]);
	system("pause");
	return 0;

3.2查找元素

#include 
#include 
using namespace std;
int main()
{
	int n, x,index=-1;
	int num[1001];
	scanf("%d", &n);
	for (int i = 0; i < n; ++i) {
		scanf("%d", &num[i]);//注意加&。
	}
	scanf("%d", &x);
	for (int i = 0; i < n; ++i) {
		if (num[i] == x) {
			index = i;
			break;
		}
	}
	printf("%d\n", index);
	system("pause");
	return 0;
}

3.3图形输出

#include 
using namespace std;
int main()
{
	char C;
	int N,row;
	scanf("%d %c", &N, &C);
	if (N % 2 == 0) {
		row = N / 2;
	}
	else {
		row = N / 2 + 1;
	}
	for (int i = 0; i < N; ++i) {
		printf("%c", C);
	}
	printf("\n");
	for (int i = 2; i < row ; ++i) {
		printf("%c", C);
		for (int j = 0; j < N-2; ++j) {
			printf(" ");
		}
		printf("%c\n", C);
	}
	for (int i = 0; i < N; ++i) {
		printf("%c", C);
	}

	system("pause");
	return 0;

3.4日期差值

#include 
#include 
using namespace std;
int month[2][12] = {
	31,28,31,30,31,30,31,31,30,31,30,31,
	31,29,31,30,31,30,31,31,30,31,30,31
};
int leap(int year) {
	return ((year % 4) && (year % 100 != 0)) || (year % 400 == 0);
}
int main()
{
	int day ;
	int time1,time2,startyear,endyear, startmonth,endmonth, startday,endday;
	while (scanf("%d%d", &time1, &time2) != EOF) {
		day = 1;
		if (time1 > time2) {
			swap(time1, time2);
		}
		startyear = time1 / 10000, startmonth = time1 % 10000 / 100, startday = time1 % 100;
		endyear = time2 / 10000, endmonth = time2 % 10000 / 100, endday = time2 % 100;
		while (startyear < endyear || startmonth < endmonth || startday < endday) {
			startday++;
			if (startday == month[leap(startyear)][startmonth] + 1) {
				++startmonth;
				startday = 1;
			}
			if (startmonth == 13) {
				++startyear;
				startmonth = 1;
			}
			++day;
		}

		printf("%d\n", day);
	}
	system("pause");
	return 0;
}

3.5进制转换

#include 
#include 
using namespace std;

int main()
{
	int A, B,D,num,index=0;
	int z[40] ;
	scanf("%d%d%d", &A, &B,&D);
	num = A + B;
	do{
		z[index++] = num%D;
		num /= D;
	} while (num);
	for (int i = index-1; i>=0; --i) {
		printf("%d", z[i]);
	}
	printf("\n");
	system("pause");
	return 0;
}

3.6字符串处理

#include 
#include 
#include 
using namespace std;

int main()
{
	string s;
	bool flag = true;
	cin >> s;
	for (int i = 0, j = s.length() - 1; i < j; ++i, --j) {
		if (s[i] != s[j]) {
			flag = false;
			break;
		}
	}
	if (flag) {
		printf("YES\n");
	}
	else {
		printf("NO\n");
	}
	system("pause");
	return 0;
}

#include 
#include 
#include 
using namespace std;
void Reverse(string &s,int left,int right) {
	while (left < right) {
		swap(s[left++], s[right--]);
	 }
}
int main()
{
	string s;
	int i, j, k=0;
	getline(cin, s);
	Reverse(s,0,s.length()-1);
	for (i=0 ; i