是否可以從給定字串形成長度不限的所有可能字串?
在本節中,我們將瞭解如何生成長度不限的所有可能字串,它將採用各種字元組合來生成字串。例如,如果字串為 ABC,則它會生成 − {A,B,C,AB,BA,BC,CB,CA,AC,ABC,ACB,BAC,BCA,CAB,CBA}
我們看一個例子來幫助理解。
演算法
printAllString(str)
Begin n := length of the string str count is 2^n – 1 for each number 0 to count, do sub_str := empty string for j in range 0 to n, do if jth bit of the counter is set, then concatenate jth character of str with sub_str end if done repeat: print sub_string until next permutation of sub_string is not completed done End
示例
#include <iostream> #include <algorithm> #include <cmath> using namespace std; void printAllString(string str) { int n = str.size(); unsigned int count = pow(2, n); for (int counter = 1; counter <count; counter++) { //generate 2^n - 1 strings string subs = ""; for (int j = 0; j < n; j++) { if (counter & (1<<j)) //when the jth bit is set, then add jth character subs.push_back(str[j]); } do{ cout << subs << endl; } while (next_permutation(subs.begin(), subs.end())); } }
輸出
A B AB BA C AC CA BC CB ABC ACB BAC BCA CAB CBA D AD DA BD DB ABD ADB BAD BDA DAB DBA CD DC ACD ADC CAD CDA DAC DCA BCD BDC CBD CDB DBC DCB ABCD ABDC ACBD ACDB ADBC ADCB BACD BADC BCAD BCDA BDAC BDCA CABD CADB CBAD CBDA CDAB CDBA DABC DACB DBAC DBCA DCAB DCBA
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