C++實現(xiàn)將一個字符串中的字符替換成另一個字符串的方法
本文實例講述了C++實現(xiàn)將一個字符串中的字符替換成另一個字符串的方法,分享給大家供大家參考。具體方法如下:
題目要求:
原地實現(xiàn)字符串中的每個空格替換成"%20",例如輸入"We are happy", 輸出"We%20are%20happy"
被替換的字符串當(dāng)然不僅僅是空格,上面只是個例子
這是道很好的題目,也是百度面試中的一道題,題目不難,但是問題得考慮全面。這里給出如下實現(xiàn)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: 只有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: 正常情況 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: 空格在后 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: 兩邊一樣 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; }
分析上述代碼,很有意思的一個情況是srcLen和destLen或大或小的情形,其邊界條件的判定不一樣。比如we are happy為例子,從后往前拷貝時,count=2。
在count=0時,恰好將最前面的空格替換完成,we則不用重復(fù)拷貝。但是對于從前往后拷貝,當(dāng)count=0時,最后面的happy將不會被拷貝。
希望本文所述實例對大家C++程序算法設(shè)計的學(xué)習(xí)有所幫助。
相關(guān)文章
C++使用expected實現(xiàn)優(yōu)雅的錯誤處理
C++ 中提供了很多中方式進(jìn)行錯誤處理。無論是通過拋異常還是通過錯誤碼,標(biāo)準(zhǔn)庫都提供相應(yīng)的調(diào)用,今天本文為大家介紹的是使用expected進(jìn)行錯誤處理,感興趣的可以了解一下2023-06-06VC6.0打開文件以及向工程中添加文件時程序崩潰自動退出解決方法
vc6.0程序中,點擊打開文件以及向工程中添加文件時,程序竟然崩潰自動退出了,不知什么原因,安裝相同的vc程序,本本竟然出現(xiàn)此緣故2013-01-01C++開發(fā)在IOS環(huán)境下運行的LRUCache緩存功能
本文著重介紹如何在XCODE中,通過C++開發(fā)在IOS環(huán)境下運行的緩存功能。算法基于LRU,最近最少使用,需要的朋友可以參考下2012-11-11