2017-09-08 LeetCode_006 ZigZag Conversion

6. ZigZag Conversion

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   NA P L S I I GY   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 text, int nRows);

convert("PAYPALISHIRING", 3) should return "PAHNAPLSIIGYIR".

solution:

class Solution {

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public:

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    string convert(string s, int numRows) {

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        string ans;

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        int l = s.length(), n = numRows;

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        int m = (n == 1 ? 1 : 2*n-2);

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        int k = l/m, r = l%m;

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        for (int i = 0; i < n; i++)

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            if (i == 0) {

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                int max = (r == 0 ? k : k+1);

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                for (int j = 0; j < max; j++) ans += s[j*m];

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            } else if (i == n-1) {

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                int max = (r <= n-1 ? k : k+1);

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                for (int j = 0; j < max; j++) ans += s[j*m+n-1];

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            } else {

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                int max;

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                if (r <= i) max = 2*k;

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                else if (i < r && r <= m-i) max = 2*k+1;

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                else max = 2*k+2;

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                for (int j = 0; j < max; j++)

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                    if (j%2 == 0) ans += s[(int)(j/2)*m+i];

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                    else ans += s[(int)(j/2)*m+m-i];

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            }

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        return ans;

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    }

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};