6. Zigzag Conversion

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problem

solution

mod

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class Solution {
public:
    string convert(string s, int numRows) {
        if(numRows==1) return s;
        vector<string> nums(numRows);
        int period = 2*numRows-2;
        for(int i=0;i<s.size() ; ++i){
            int mod = i%period;
            if(mod < numRows) nums[mod]+=s[i];
            else nums[period-mod]+=s[i];
        }
        string ret;
        for(string str:nums) ret+=str;
        return ret;
    }
};

analysis

  • time complexity O(n)
  • space complexity O(n)