一道小學數學題:ZigZag Conversion
阿新 • • 發佈:2018-12-05
題目描述
The string “PAYPALISHIRING” is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)
P A H N
A P L S I I G
Y I R
And then read line by line: "PAHNAPLSIIGYIR"
Write the code that will take a string and make this conversion given a number of rows:
string convert(string s, int numRows);
通俗一點來說,就是將給定字串以N字形輸出之後再去掉空格回車按行順序得到一個全新的字串。
來看幾個例子:
Example 1:
Input: s = "PAYPALISHIRING", numRows = 3
Output: "PAHNAPLSIIGYIR"
---
Example 2:
Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:
P I N
A L S I G
Y A H R
P I
求解演算法
一開始沒有注意到要去掉空格,發現之後全都註釋掉對應部分就過了。思路很簡單,就是發現規律而已。
class Solution {
public:
string convert(string s, int numRows) {
if (numRows == 1) {
return s;
}
int L = s.length();
int a = L/(2*numRows-2), b = L%(2*numRows-2);
int numCols = a*(numRows-1)+1+b/numRows*(b%numRows);
string ss = "";
int index = 0;
for (int i = 0; i < numRows; i++) {
for (int j = 0; j < numCols; j++) {
a = j%(numRows-1);
if (a > 0 && a+i != numRows-1) {
//ss += " ";
}
else {
b = j/(numRows-1);
index = b*(2*numRows-2)+(a==0?i:numRows+a-1);
if (index < s.length()) {
ss += s[index] ;
}
/*else {
ss += ' ';
}*/
}
}
//ss += '\n';
}
return ss;
}
};
其實還有一種思路就是,先獲得每一列對應的字串,然後按行拼接起來,這樣很容易實現,但是複雜度就上去了。