C++——一些小功能【简单实现】-创新互联

ifstream ifs("1.txt");
 if (ifs.is_open()) { ifs.seekg(0, ios::end);
     streamoff len = ifs.tellg(); // streamoff  == long long
     cout<< len<< endl;
 }
 ifs.close();

void split(const string& line, const string& delim, vector& arr)
{int start = 0;
    int pos = 0;
    while (line.find(delim, start) != string::npos) {pos = line.find(delim, start);
        arr.push_back(line.substr(start, pos - start));
        start = pos + delim.size();
    }
    if (start< line.size()) {arr.push_back(line.substr(start));
    }
}

string strip(const string& line)
{int pos_start = line.find_first_not_of(" \r\n\t");
    int pos_end = line.find_last_not_of(" \r\n\t");
    if (pos_start == string::npos || pos_end == string::npos) {return line;    
    }
    string res = line.substr(pos_start, pos_end - pos_start + 1);
    int pos = res.find("  ");
    while (pos != -1) {res.replace(pos, 2, " ");
        pos = res.find("  ", pos);
    }
    return res;
}

templatevoid selectionSort(T &arr, FUNC func)
{int n = static_cast(arr.size());
    for (int i = 0; i< n - 1; ++i) {int idx = i;
        for (int j = i + 1; j< n; ++j) {if (func(arr[j], arr[idx])) {idx = j;
            }
        }
        swap(arr[idx], arr[i]);
    }
}

templatevoid bubbleSort(T &arr, FUNC func)
{int n = static_cast(arr.size());
    for (int i = 0; i< n - 1; ++i) {bool flag = false;
        for (int j = 0; j< n - 1 - i; ++j) {if (func(arr[j + 1], arr[j])) {swap(arr[j + 1], arr[j]);
                flag = true;
            }
        }
        if (flag) {break;
        }
    }
}

templatevoid insertionSort(T &arr, FUNC func)
{int n = static_cast(arr.size());
    for (int i = 0; i< n; ++i) {int j = i;
        auto tmp = arr[i];
        while (j--) {if (func(tmp, arr[j])) {arr[j + 1] = arr[j];
            } else {break;
            }
        }
        arr[j + 1] = tmp;
    }
}

templatevoid quickSort(T &arr, int start, int end, FUNC func)
{int right = end;
    int left = start;
    auto key = arr[start];
    while (left< right) {while (left< right && !func(arr[right], key)) {--right;
        }
        arr[left] = arr[right];
        while (left< right && func(arr[left], key)) {++left;
        }
        arr[right] = arr[left];
    }
    arr[left] = key;
    if (start< right) {quickSort(arr, start, right - 1, func);
    }
    if (left< end) {quickSort(arr, left + 1, end, func);
    }
}

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