11.用連結串列模擬大整數加法運算
阿新 • • 發佈:2019-01-09
例如:9->9->9->NULL
+ 1->NULL
1->0->0->0->NULL
思路:
使用遞迴,能夠實現從前往後計算。
// LinkTable.cpp : 定義控制檯應用程式的入口點。 // #include "stdafx.h" #include <iostream> #include <string> using namespace std; //連結串列的結構體 struct node { char val; node * next; }; //建立連結串列 struct node * create( string & str_link ) { int len = str_link.length(); struct node * phead = new node(); //帶有表頭的連結串列,表頭中不儲存任何元素 struct node * preNode = phead; for( int i=0; i<len; i++ ) { struct node * pNode = new node(); pNode->val = str_link[i]; pNode->next = NULL; preNode->next = pNode; preNode = pNode; } return phead; } //輸出連結串列 void out_link( struct node * phead ) { if( phead == NULL ) return; struct node * pNode = phead->next; while( pNode ) { cout <<pNode->val; pNode = pNode->next; } cout << endl; } //求無表頭連結串列的長度 //返回-1為連結串列不存在 int link_length( struct node* pNode ) { if(!pNode) return -1; int len=0; while( pNode ) { pNode = pNode->next; len++; } return len; } //大數相加遞迴演算法 //pNode1, pNode2為兩個中間運算結點,但不是頭結點 struct node * add( struct node * pNode1, struct node * pNode2, int & carry ) { if( !pNode1 ) return pNode2; if( !pNode2 ) return pNode1;
//為了引數簡潔,這裡增大了計算量,可以將連結串列長度作為引數傳進來 int len1 = link_length( pNode1 ); int len2 = link_length( pNode2 ); if( len1 == len2 ) { if( len1==1 ) //遞迴終止條件 { struct node * pNode = new node(); int sum = (pNode1->val - '0' ) + ( pNode2->val -'0'); carry = sum/10; pNode->val = sum%10 + '0'; pNode->next = NULL; return pNode; } else { int carry_cur=0; struct node * pNode = new node(); struct node * pNext = add( pNode1->next, pNode2->next, carry_cur ); int sum = (pNode1->val - '0' ) + ( pNode2->val -'0') + carry_cur; carry = sum/10; pNode->val = sum%10 + '0'; pNode->next = pNext; return pNode; } } if( len1>len2 ) { int carry_cur=0; struct node * pNode = new node(); struct node * pNext = add( pNode1->next, pNode2, carry_cur ); int sum = (pNode1->val - '0' ) + carry_cur; carry = sum/10; pNode->val = sum%10 + '0'; pNode->next = pNext; return pNode; } if( len1<len2 ) { int carry_cur=0; struct node * pNode = new node(); struct node * pNext = add( pNode1, pNode2->next, carry_cur ); int sum = (pNode2->val - '0' ) + carry_cur; carry = sum/10; pNode->val = sum%10 + '0'; pNode->next = pNext; return pNode; } return NULL; } struct node * add( struct node * phead1, struct node * phead2 ) { if( !phead1 || !phead1->next ) return phead2; if( !phead2 || !phead2->next ) return phead1; int carry = 0; struct node * pNode = add( phead1->next, phead2->next, carry ); if( carry > 0 ) //有進位,則需要多一個結點 { struct node * pCarry = new node(); pCarry->val = '0' + carry; pCarry->next = pNode; pNode = pCarry; } struct node * phead = new node(); phead->next = pNode; return phead; } void test() { string str; cout << "Input the first link:"<<endl; cin >> str; struct node *phead1 = create( str ); cout << "Input the second link:"<<endl; cin >> str; struct node *phead2 = create( str ); struct node * phead = add( phead1, phead2); cout<< "The result is:" <<endl; out_link( phead ); } int _tmain(int argc, _TCHAR* argv[]) { test(); return 0; }