100000580 - 《算法笔记》3.6小节——入门模拟->字符串处理

《算法笔记》3.6小节——入门模拟->字符串处理

疑问：
1962 Problem D和1963 Problem E 都是：不加getchar()正确50%，加上后正确100%

PAT B1009 【说反话】20分
pat的C++编译器不让用gets函数？
scanf遇到空格或\n结束； gets遇到\n结束.

#include<cstdio>
#include<cstring>

int main() {
	char str[100];
	while (gets_s(str)) {
		char trans[80][80];
		int len = strlen(str);
		int num = 0, j = 0;
		for (int i = 0; i <len; i++) {
			if (str[i] != ' ') trans[num][j++] = str[i];
			else {
				//每个单词结束时要在结尾加结束字符
				trans[num][j] = '\0';
				num++; j = 0;
			}
		}
		trans[num][j] = '\0';

		for (int i = num; i >=0; i--) {
			printf("%s",trans[i]);
			if (i != 0)printf(" ");
			else printf("\n");
		}
	}
	
	return 0;
}

1785 Problem A 字符串连接

#include<cstdio>
#include<cstring>

int main() {
	char a[200], b[100];
	while (scanf("%s %s", &a, &b) != EOF) {
		int lena = 0 , lenb = 0;
		while (a[lena] != '\0') lena++;
		while (b[lenb] != '\0') lenb++;
	//注意字符串末尾的'\0'			
		for (int i = 0; i < lenb; i++) {
			a[lena + i] = b[i];
		}
		lena += lenb;
		a[lena] = '\0';
		printf("%s\n", a);
		//或者把b字符串的末尾'\0'也复制到a的末尾，即
		//for (int i = 0; i <= lenb; i++) {
		//	a[lena + i] = b[i];
		//}
		//printf("%s\n", a);
	}

	return 0;
}

1805 Problem B 首字母大写
vs17用不了gets()，要用gets_s()

#include<cstdio>
#include<cstring>

int main() {
	//通过gets读入一整行字符
	char str[100];
	while (gets_s(str) ) {
		if ((str[0] >= 97 && str[0] <= 122)) str[0] -= 32;
		for (int i = 1; i < strlen(str); i++) {
			//不确定优先级的一定要加括号，不加括号容易错
						if((str[i-1]==' ' ||str[i-1]=='\t'|| str[i-1]=='\r' || str[i-1]=='\n') &&(str[i]>=97 && str[i]<=122))
				str[i]-=32;			
		}
		puts(str);
	}

	return 0;
}

或者用flag记录str[i-1]是否是特殊符号

#include<cstdio>
#include<cstring>

int main() {
	//通过gets读入一整行字符
	char str[100];
	while (gets_s(str) ) {
		int flag = 0;
		
		for (int i = 0; i < strlen(str); i++) {
			if (str[i] == ' ' || str[i] == '\t' || str[i] == '\r' || str[i] == '\n')
				flag = 0;
			else {
				if (flag == 0 && (str[i] >= 97 && str[i] <= 122))
					str[i] -= 32;
				flag = 1;
			}

		}
		puts(str);
	}

	return 0;
}

1808 Problem C 字符串的查找删除
半成品

#include<cstdio>
#include<cstring>
/*
int KMP(char S[], char T[], int next[], int pos) {
	int i = pos;
	int j = 0;
	for (int i = 0; i < strlen(S); i++) {
		if (S[i] >= 'A'&& S[i] <= 'Z') S[i] = S[i] + 32;
	}
	while (i <= strlen(S) && j <= strlen(T)) {
		if (j == 0 || S[i] == T[j]) {
			i++; j++;
		}
		else {
			j = next[j];
		}
	}
	if (j > 0) return i - strlen(T);
	else return -1;
}
void get_next(char T[], int next[]) {
	int i = 0, j = 0;
	next[1] = 0;
	while (i < strlen(T)) {
		if (j == 0 || T[i] == T[j]) {
			next[i] = j;
			i++; j++;
		}
		else {
			j = next[j];
		}
	}
}
*/
int main() {
	char del[20];
	scanf("%s", &del);
	for (int i = 0; i < strlen(del); i++) {
		if (del[i] >= 'A'&&del[i] <= 'Z') del[i] = del[i] + 32;
	}
	int lendel = strlen(del);
	//注意大写小写In、IN、iN、in都要删除
	
	//第一步删除所有空格
	//第二步将字符串先做统一化处理，用KMP算法找出匹配位置，删除或打印时略过
	char str[50];
	while (scanf("%s", &str) != EOF) {
		int temp = 0,len = 0;
		for (len = 0; len < strlen(str)-temp; len++) {
			if (str[len] == ' ') {
				temp++;
				str[len] = str[len + temp];
			}
		}
		str[len] = '\0';
		
		int num = 0;
		
		
		if (num == -1) printf("%s", str);
		else {
			for (int i = 0; i <len; i++) {
				if (i < num || i >= (num + strlen(del)))
					printf("%c", str[i]);
			}
			printf("\n");
		}
	}
	return 0;
} 

1962 Problem D 单词替换
最后一个getchar()，否则要输两次Ctrl+Z才能结束
也避免多余的符号被gets进s

#include <stdio.h>
#include <string.h>

int main() {
	char s[120], a[120], b[120];

	while (gets_s(s)) {
		
		char arr[120][120];
		int num = 0, j = 0;
		for (int i = 0; i < strlen(s); i++) {
			if (s[i] == ' ') {
				arr[num][j] = '\0';
				num++; j = 0;
			}
			else {
				arr[num][j++] = s[i];
			}
		}
		arr[num][j] = '\0';

		scanf("%s", &a);
		scanf("%s", &b);

		for (int i = 0; i <= num; i++) {
			if (strcmp(a, arr[i]) == 0) strcpy(arr[i], b);
			printf("%s", arr[i]);
			if(i== num)  printf("\n");
			else printf(" ");
		}
		
		//memset(s, '\0', sizeof(s));
		//memset(a, '\0', sizeof(a));
		//memset(b, '\0', sizeof(b));
		getchar();
	}

	return 0;
}

1963 Problem E 字符串去特定字符
%s通过空格和换行来识别一个字符串的结束，%c是可以匹配空格的
另开数组，用空间换时间

#include <stdio.h>
#include <string.h>

int main() {
	char s[400];
	char c;
	while (gets_s(s)){
		scanf("%c", &c);
		char temp[400];
		int len = 0;
		for (int i = 0; i < strlen(s); i++) {
		//for (int i = 0; s[i] != '\0'; i++) 
			if (s[i] != c) 
				temp[len++] = s[i];
		}
		temp[len] = '\0';
		printf("%s\n", temp);
		memset(temp, '\0', sizeof(temp));
		getchar();
	}

	return 0;
}

1967 Problem F 数组逆置

#include <stdio.h>
#include <string.h>
#include<algorithm>
using namespace std;

int main() {
	char str[210];
	while (gets(str)) {
		int len = strlen(str);
		for (int i = 0; i < len/2; i++) {
			swap(str[i], str[len - 1 - i]);
		}
		printf("%s\n", str);
	}
	return 0;
}

2025 Problem G 比较字符串

#include <stdio.h>
#include <string.h>

int main() {
	int m = 0;
	scanf("%d", &m);
	while(m--) {
		char a[60], b[60];
		scanf("%s %s", &a, &b);
		if (strlen(a) > strlen(b)) printf("%s is longer than %s\n",a,b);
		else if (strlen(a) == strlen(b)) printf("%s is equal long to %s\n",a,b);
		else printf("%s is shorter than %s\n",a,b);

	}
	return 0;
}

2064 Problem H 编排字符串

#include <stdio.h>
#include <string.h>

int main() {
	char a[100][25];
	int m = 0;
	scanf("%d", &m);
	for (int i = 0; i < m; i++) {
		scanf("%s", a[i]);
		for (int j = i; j >= 0&&i-j+1<=4; j--) {
			printf("%d=%s", i - j + 1, a[j]);
			if (j != 0 || (j == 0 && i == 0)) printf(" ");
		}
		printf("\n");
	}
	return 0;
}

5901 Problem I 【字符串】回文串

#include<cstdio>
#include<cstring>

int main() {
	char str[260];
	while (scanf("%s", &str) != EOF) {
		bool flag = true;
		for (int i = 0; i < strlen(str)/2; i++) {
			if (str[i] != str[strlen(str) - 1 - i]) {
				flag = false;
				break;
			}
		}
		if (flag == true) printf("YES\n");
		else printf("NO\n");
	}

	return 0;
}