标签:11 case 21 ix ++ 5th break int sum
练习5.11 修改统计元音字母的程序,使其也能统计空格、制表符、和换行符的数量。
#include<iostream>
#include<string>
using namespace std;
int main()
{
string s;
int sum_a = 0, sum_e = 0, sum_i = 0, sum_o = 0, sum_u = 0,
sum_space = 0, sum_tab = 0, sum_enter = 0;
int vowelcnt = 0;
while(getline(cin, s)){
for(auto ch: s)
switch (ch)
{
case 'a':
case 'A':
++sum_a;
++vowelcnt;
break;
case 'e':
case 'E':
++sum_e;
++vowelcnt;
break;
case 'i':
case 'I':
++sum_i;
++vowelcnt;
break;
case 'o':
case 'O':
++sum_o;
++vowelcnt;
break;
case 'u':
case 'U':
++sum_u;
++vowelcnt;
break;
case ' ':
++sum_space;
break;
case '\t':
++sum_tab;
break;
default:
break;
}
++sum_enter;
}
cout << "acnt is: " << sum_a << endl;
cout << "ecnt is: " << sum_e << endl;
cout << "icnt is: " << sum_i << endl;
cout << "ocnt is: " << sum_o << endl;
cout << "ucnt is: " << sum_u << endl;
cout << "spacecnt is: " << sum_space << endl;
cout << "tabcnt is: " << sum_tab << endl;
cout << "entercnt is: " << sum_enter << endl;
cout << "vowelcnt is: " << vowelcnt << endl;
return 0;
}
练习5.12 修改统计元音字母的程序,使其能统计含以下两个字符的字符序列的数量: ff、fl和fi。
#include<iostream>
#include<string>
using namespace std;
int main()
{
string s;
int sum_a = 0, sum_e = 0, sum_i = 0, sum_o = 0, sum_u = 0,
sum_space = 0, sum_tab = 0, sum_enter = 0, sum_ff = 0, sum_fl = 0, sum_fi = 0;
int vowelcnt = 0;
char prech = '\0';
while (getline(cin, s)) {
for (auto ch : s) {
switch (ch)
{
case 'a':
case 'A':
++sum_a;
++vowelcnt;
break;
case 'e':
case 'E':
++sum_e;
++vowelcnt;
break;
case 'i':
if (prech == 'f') ++sum_fi;
case 'I':
++sum_i;
++vowelcnt;
break;
case 'o':
case 'O':
++sum_o;
++vowelcnt;
break;
case 'u':
case 'U':
++sum_u;
++vowelcnt;
break;
case ' ':
++sum_space;
break;
case '\t':
++sum_tab;
break;
case 'f':
if (prech == 'f') ++sum_ff;
break;
case 'l':
if (prech == 'f') ++sum_fl;
break;
default:
break;
}
prech = ch;
}
++sum_enter;
}
cout << "acnt is: " << sum_a << endl;
cout << "ecnt is: " << sum_e << endl;
cout << "icnt is: " << sum_i << endl;
cout << "ocnt is: " << sum_o << endl;
cout << "ucnt is: " << sum_u << endl;
cout << "spacecnt is: " << sum_space << endl;
cout << "tabcnt is: " << sum_tab << endl;
cout << "entercnt is: " << sum_enter << endl;
cout << "vowelcnt is: " << vowelcnt << endl;
cout << "ff cnt is: " << sum_ff << endl;
cout << "fi cnt is: " << sum_fi << endl;
cout << "fl cnt is: " << sum_fl << endl;
return 0;
}
练习5.13 下面显示的每个程序都含有一个常见的编码错误,指出错误在哪里,然后修改它们。
(a) unsigned aCnt = 0, eCnt = 0, iouCnt = 0;
char ch = next_text();
switch (ch) {
case 'a': aCnt++;
case 'e': eCnt++;
default: iouCnt++;
}
(b) unsigned index = some_value();
switch (index) {
case 1:
int ix = get_value();
ivec[ ix ] = index;
break;
default:
ix = ivec.size()-1;
ivec[ ix ] = index;
}
(c) unsigned evenCnt = 0, oddCnt = 0;
int digit = get_num() % 10;
switch (digit) {
case 1, 3, 5, 7, 9:
oddcnt++;
break;
case 2, 4, 6, 8, 10:
evencnt++;
break;
}
(d) unsigned ival=512, jval=1024, kval=4096;
unsigned bufsize;
unsigned swt = get_bufCnt();
switch(swt) {
case ival:
bufsize = ival * sizeof(int);
break;
case jval:
bufsize = jval * sizeof(int);
break;
case kval:
bufsize = kval * sizeof(int);
break;
}
- (a) 少了 break语句。应该为:
unsigned aCnt = 0, eCnt = 0, iouCnt = 0;
char ch = next_text();
switch (ch) {
case 'a':
aCnt++;
break;
case 'e':
eCnt++;
break;
default:
iouCnt++;
break;
}
- (b) 在 default 分支当中,ix 未定义。应该在外部定义ix。
unsigned index = some_value();
int ix;
switch (index) {
case 1:
ix = get_value();
ivec[ ix ] = index;
break;
default:
ix = static_cast<int>(ivec.size())-1;
ivec[ ix ] = index;
}
- © case 后面应该用
:
而不是,
。
unsigned evenCnt = 0, oddCnt = 0;
int digit = get_num() % 10;
switch (digit) {
case 1: case 3: case 5: case 7: case 9:
oddcnt++;
break;
case 2: case 4: case 6: case 8: case 0:
evencnt++;
break;
}
- (d) case 标签必须是整型常量表达式。
const unsigned ival=512, jval=1024, kval=4096;
unsigned bufsize;
unsigned swt = get_bufCnt();
switch(swt) {
case ival:
bufsize = ival * sizeof(int);
break;
case jval:
bufsize = jval * sizeof(int);
break;
case kval:
bufsize = kval * sizeof(int);
break;
}
**练习5.14 **
#include<iostream>
#include<string>
using namespace std;
int main()
{
string s;
string bef = "", mts = "";
int msum = 0, sum = 0;
while(cin >> s){
if (s == bef) {
++sum;
if (msum < sum) {
msum = sum;
mts = s;
}
}
else {
sum = 1;
bef = s;
}
}
cout << mts <<" occurred cnt is: " << sum << endl;
return 0;
}
练习5.15 说明下列循环的含义并改正其中的错误。
(a) for (int ix = 0; ix != sz; ++ix) { /* ... */ }
if (ix != sz)
// . . .
(b) int ix;
for (ix != sz; ++ix) { /* ... */ }
(c) for (int ix = 0; ix != sz; ++ix, ++sz) { /*...*/ }
改正:
(a) int ix;
for (ix = 0; ix != sz; ++ix) { /* ... */ }
if (ix != sz)
// . . .
(b) int ix;
for (ix = 0;ix != sz; ++ix) { /* ... */ }
(c) for (int ix = 0; ix != sz; ++ix) { /*...*/ }
练习5.16 while 循环特别适用于那种条件不变、反复执行操作的情况,例如,当未达到文件末尾时不断读取下一个值。for 循环更像是在按步骤迭代,它的索引值在某个范围内一次变化。根据每种循环的习惯各自编写一段程序,然后分别用另一种循环改写。如果只能使用一种循环,你倾向于哪种?为什么?
//反复操作
while (cin >> s) {
//...
}
for (;cin >> s;) {
//...
}
//迭代
for (int i = 0; i < s.size(); ++i) {
//...
}
int i = 0;
while (i < s.size()) {
//...
++i;
}
我更倾向于保留for,因为它写法更紧凑,利于读者了解循环的目的。
练习5.17 假设有两个包含整数的vector对象,编写一段程序,检验其中一个vector对象是否是另一个的前缀。为了实现这一目标,对于两个不等长的vector对象,只需挑出长度较短的那个,把它的所有元素和另一个vector对象比较即可。例如,如果两个vector对象的元素分别是0、1、1、2 和 0、1、1、2、3、5、8,则程序的返回结果为真。
bool ispre(vector<int> &a, vector<int> &b) {
bool flag = true;
int sz = min(a.size(), b.size());
for (int i = 0; i < sz; ++i) {
if (a[i] != b[i]) {
flag = false; break;
}
}
return flag;
}
练习5.18 说明下列循环的含义并改正其中的错误。
(a) do { // 应该添加花括号
int v1, v2;
cout << "Please enter two numbers to sum:" ;
if (cin >> v1 >> v2)
cout << "Sum is: " << v1 + v2 << endl;
}while (cin);
(b) int ival;
do {
// . . .
} while (ival = get_response()); // 应该将ival 定义在循环外
(c) int ival = get_response();
do {
ival = get_response();
} while (ival); // 应该将ival 定义在循环外
练习5.19 编写一段程序,使用do while 循环重复地执行下述任务:首先提示用户输入两个string对象,然后挑出较短的那个并输出它。
#include<iostream>
#include<string>
#include<vector>
using namespace std;
int main()
{
string s1, s2;
do {
cout << "Please input two string" << endl;
cin >> s1 >> s2;
cout << ((s1.size() <= s2.size()) ? s1 : s2) << endl;
cout << "continue? Enter yes or no: ";
cin >> s1;
} while (!s1.empty() && s1[0] != 'n');
return 0;
}
**练习5.20 **
#include<iostream>
#include<string>
#include<vector>
using namespace std;
int main()
{
string s, pres="";
bool flag = true;
while (cin >> s) {
if (s == pres) {
flag = false;
break;
}
pres = s;
}
if(flag)
cout << "no word was repeated." << endl;
else {
cout << s << " occurs twice in succession." << endl;
}
return 0;
}
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标签:11,case,21,ix,++,5th,break,int,sum 来源: https://blog.csdn.net/qq_40758751/article/details/104099700
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