C++完成將一個字符串中的字符調換成另外一個字符串的辦法。本站提示廣大學習愛好者:(C++完成將一個字符串中的字符調換成另外一個字符串的辦法)文章只能為提供參考,不一定能成為您想要的結果。以下是C++完成將一個字符串中的字符調換成另外一個字符串的辦法正文
本文實例講述了C++完成將一個字符串中的字符調換成另外一個字符串的辦法,分享給年夜家供年夜家參考。詳細辦法以下:
標題請求:
原地完成字符串中的每一個空格調換成"%20",例如輸出"We are happy", 輸入"We%20are%20happy"
被調換的字符串固然不只僅是空格,下面只是個例子
這是道很好的標題,也是百度面試中的一道題,標題不難,然則成績得斟酌周全。這裡給出以下完成代碼:
#include <iostream> #include <vector> #include <cassert> using namespace std; int findNumberFirst(const char *str, const char *dest, vector<int>& pvec) { if (str == NULL || dest == NULL) return 0; int pos = 0; int lenStr = strlen(str); int lenDest = strlen(dest); if (lenStr < lenDest) return 0; int count = 0; while (pos <= lenStr - lenDest) { if (strncmp(str + pos, dest, strlen(dest)) == 0) { pvec.push_back(pos); pos += lenDest; count++; } else { pos++; } } return count; } int findNumberLast(const char *str, const char *dest, vector<int> &pvec) { if (str == NULL || dest == NULL) return 0; int strLen = strlen(str); int destLen = strlen(dest); if (strLen < destLen) return 0; int pos = 0; while (pos <= strLen - destLen) { if (strncmp(str + pos, dest, strlen(dest)) == 0) { pos += destLen; pvec.push_back(pos - 1); } else { pos++; } } return pvec.size(); } void replaceArray(char *str, const char *src, const char *dest) { if (str == NULL || src == NULL || dest == NULL) return; vector<int> pvec; int strLen = strlen(str); int srcLen = strlen(src); int destLen = strlen(dest); if (strLen < srcLen) return; int posBefore = 0; int posAfter = 0; if (srcLen < destLen) { int count = findNumberLast(str, src, pvec); if (count <= 0) return; posAfter = strLen + count * (destLen - srcLen) - 1; posBefore = strLen - 1; while (count > 0 && posBefore >= 0) { if (pvec[count - 1] == posBefore) { posAfter -= destLen; strncpy(str + posAfter + 1, dest, strlen(dest)); count--; posBefore--; } else { str[posAfter--] = str[posBefore--]; } } } else if (strLen > destLen) { int count = findNumberFirst(str, src, pvec); if (count <= 0) return; posAfter = 0; posBefore = 0; int i = 0; while (count >= 0 && posBefore < strLen) { if (count > 0 && pvec[i] == posBefore) { strncpy(str + posAfter, dest, strlen(dest)); posAfter += destLen; count--; posBefore += srcLen; i++; } else { str[posAfter++] = str[posBefore++]; } } str[posAfter] = '\0'; } } void main() { char *str = new char[100]; if (str == NULL) return; memset(str, '\0', 100); const char *src = " "; const char *dest = "%20"; //case1: 只要1個空格 strcpy(str, " "); replaceArray(str, src, dest); cout << "str: " << str << endl; replaceArray(str, dest, src); cout << "str: " << str << endl; //case2: 兩個空格 strcpy(str, " "); replaceArray(str, src, dest); cout << "str: " << str << endl; replaceArray(str, dest, src); cout << "str: " << str << endl; //case3: 正常情形 strcpy(str, "we are happy"); replaceArray(str, src, dest); cout << "str: " << str << endl; replaceArray(str, dest, src); cout << "str: " << str << endl; //case3: 空格在前 strcpy(str, " we are happy"); replaceArray(str, src, dest); cout << "str: " << str << endl; replaceArray(str, dest, src); cout << "str: " << str << endl; //case4: 空格在後 strcpy(str, "we are happy "); replaceArray(str, src, dest); cout << "str: " << str << endl; replaceArray(str, dest, src); cout << "str: " << str << endl; //case4: 沒空格 strcpy(str, "wearehappy"); replaceArray(str, src, dest); cout << "str: " << str << endl; replaceArray(str, dest, src); cout << "str: " << str << endl; //case5: 雙方一樣 strcpy(str, "we are happy"); replaceArray(str, src, dest); cout << "str: " << str << endl; src = "%20"; assert(dest == "%20"); replaceArray(str, dest, src); cout << "str: " << str << endl; }
剖析上述代碼,很成心思的一個情形是srcLen和destLen或年夜或小的情況,其界限前提的剖斷紛歧樣。好比we are happy為例子,從後往前拷貝時,count=2。
在count=0時,正好將最後面的空格調換完成,we則不消反復拷貝。然則關於早年往後拷貝,當count=0時,最初面的happy將不會被拷貝。
願望本文所述實例對年夜家C++法式算法設計的進修有所贊助。