首先我是这么写的：

#include <iostream>
#include <string>


using namespace std;


char maps[114][210];
bool is_used[114][210];
int shifts[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
int ans;
int n;
string in;

void dfs(int x, int y){
	for(int i=0; i<4; i++){
		int nowx = x + shifts[i][0];
		int nowy = y + shifts[i][1];
		if(nowx>=1 and nowy>=1 and maps[nowx][nowy]>='a' and maps[nowx][nowy]<='z' and !is_used[nowx][nowy]){
			is_used[nowx][nowy] = true;
			dfs(nowx, nowy);
		}
	}
}

int main(){
	cin >> n;
	getchar();
	
	for(int i=1; i<=n; i++){
		getline(cin, in);
		int len = in.length();
		for(int j=0; j<len; j++){
			maps[i][j+1] = in[j];
		}
	}
	
	for(int i=1; i<=105; i++){
		for(int j=1; j<=205; j++){
			if(!is_used[i][j] and maps[i][j]>='a' and maps[i][j]<='z'){
				is_used[i][j] = true;
				ans++;
				dfs(i, j);
			}
		}
	}
	cout << ans;
}

AC 2, 6, 8, 10, 得40分.

于是我去看讨论区, 发现要用scanf("\n").

于是写出如下代码：

#include <iostream>
#include <string>


using namespace std;


char maps[114][210];
bool is_used[114][210];
int shifts[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
int ans;
int n;
string in;

void dfs(int x, int y){
	for(int i=0; i<4; i++){
		int nowx = x + shifts[i][0];
		int nowy = y + shifts[i][1];
		if(nowx>=1 and nowy>=1 and maps[nowx][nowy]>='a' and maps[nowx][nowy]<='z' and !is_used[nowx][nowy]){
			is_used[nowx][nowy] = true;
			dfs(nowx, nowy);
		}
	}
}

int main(){
	cin >> n;
	scanf("\n");
	
	for(int i=1; i<=n; i++){
		getline(cin, in);
		int len = in.length();
		for(int j=0; j<len; j++){
			maps[i][j+1] = in[j];
		}
	}
	
	for(int i=1; i<=105; i++){
		for(int j=1; j<=205; j++){
			if(!is_used[i][j] and maps[i][j]>='a' and maps[i][j]<='z'){
				is_used[i][j] = true;
				ans++;
				dfs(i, j);
			}
		}
	}
	cout << ans;
}

AC 1, 4, 5, 6, 7, 9, 得60分.

很气愤, 为什么连点2都过不了？

于是再敲了一个getchar()

#include <iostream>
#include <string>


using namespace std;


char maps[114][210];
bool is_used[114][210];
int shifts[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
int ans;
int n;
string in;

void dfs(int x, int y){
	for(int i=0; i<4; i++){
		int nowx = x + shifts[i][0];
		int nowy = y + shifts[i][1];
		if(nowx>=1 and nowy>=1 and maps[nowx][nowy]>='a' and maps[nowx][nowy]<='z' and !is_used[nowx][nowy]){
			is_used[nowx][nowy] = true;
			dfs(nowx, nowy);
		}
	}
}

int main(){
	cin >> n;
	getchar();getchar();
	
	for(int i=1; i<=n; i++){
		getline(cin, in);
		int len = in.length();
		for(int j=0; j<len; j++){
			maps[i][j+1] = in[j];
		}
	}
	
	for(int i=1; i<=105; i++){
		for(int j=1; j<=205; j++){
			if(!is_used[i][j] and maps[i][j]>='a' and maps[i][j]<='z'){
				is_used[i][j] = true;
				ans++;
				dfs(i, j);
			}
		}
	}
	cout << ans;
}

然后, 过了...???

求求各位dalao给出理由为什么会出现这样的情况.

所有测试皆使用c++14(gcc 9)标准.