[leetcode] Add Binary

最新推荐文章于 2018-11-29 11:33:40 发布

Cabinathor

最新推荐文章于 2018-11-29 11:33:40 发布

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分类专栏： Leetcode

本文链接：https://blog.youkuaiyun.com/lmxmimihuhu/article/details/46405079

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本文详细解析了如何将两个二进制字符串相加并返回结果字符串的方法，包括算法实现步骤和代码实例。

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From : https://leetcode.com/problems/add-binary/

Given two binary strings, return their sum (also a binary string).

For example,
a = "11"
b = "1"
Return "100".

class Solution {
public:
    string addBinary(string a, string b) {
        if(a=="0") return b;
        if(b=="0") return a;
        string ans;
        int ia = a.size()-1, ib = b.size()-1, carry = 0, va, vb;
        while(ia >= 0 || ib >= 0) {
            if(ia < 0) {va = 0; vb = b[ib]-'0';}
            else if(ib < 0) {vb = 0; va = a[ia]-'0';}
            else {va = a[ia]-'0';vb = b[ib]-'0';}
            int sum = va + vb + carry;
            switch(sum) {
                case 0: {ans = '0' + ans; carry = 0; break;}
                case 1: {ans = '1' + ans; carry = 0; break;}
                case 2: {ans = '0' + ans; carry = 1; break;}
                case 3: {ans = '1' + ans; carry = 1; break;}
            }
            ia--; ib--;
        }
        if(carry) ans = '1' + ans;
        return ans;
    }
};

public class Solution {
    public String addBinary(String a, String b) {
        if(a == null || "".equals(a)) {
            return b;
        } else if(b == null || "".equals(b)) {
            return a;
        }
        int carry = 0;
        int ia = a.length()-1, ib = b.length()-1;
        StringBuilder sb = new StringBuilder();
        
        while(ia>=0 && ib>=0) {
            int n = a.charAt(ia--)-'0'+b.charAt(ib--)-'0'+carry;
            sb.append(n&1);
            carry = n>>1;
        }
        if(ia >= 0) {
        	carry = addRest(a, ia, sb, carry);
        }
        if(ib >= 0) {
        	carry = addRest(b, ib, sb, carry);        	
        }
        if(carry > 0) {
        	sb.append('1');
        }
        return sb.reverse().toString();
    }

	private int addRest(String s, int i, StringBuilder sb, int carry) {
		while(i >= 0) {
            int n = s.charAt(i--)-'0'+carry;
            sb.append(n&1);
            carry = n>>1;
        }
		return carry;
	}
}