Multiply Strings

Author: 谭佳胜

43. Multiply Strings/index.js

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+const add = function(num1, num2) {
+    let i = num1.length - 1;
+    let j = num2.length - 1;
+    let result = '';
+    let carry = 0;
+    
+    while (i >= 0 || j >= 0) {
+        const sum = Number(num1[i] || 0) + Number(num2[j] || 0) + carry;
+        
+        result = `${sum % 10}${result}`;
+        carry = parseInt(sum / 10);
+        
+        i--;
+        j--;
+    }
+    
+    if (carry === 1) {
+        result = `1${result}`;
+    }
+    
+    return result;
+}
+const multiply = function(num1, num2) {
+    let i = num1.length;
+    let j = num2.length;
+    let carry = 0;
+    let zeros = '';
+    const resultArr = [];
+    
+    if (num1 === '0' || num2 === '0') return '0';
+    
+    for (let m = i - 1; m >= 0; m--) {
+        resultArr[m] = '';
+
+        for (let n = j - 1; n >= 0; n--) { 
+            const sum = Number(num1[m]) * Number(num2[n]) + carry;
+            
+            
+            resultArr[m] = `${sum % 10}${resultArr[m]}`;
+            carry = parseInt(sum / 10);
+        }
+        
+        if (carry > 0) {
+            resultArr[m] = `${carry}${resultArr[m]}`;
+            carry = '';
+        }
+        
+        resultArr[m] += zeros;
+        zeros += '0';
+    }
+    
+    return resultArr.reduce((pre, cur) => add(pre, cur), '');
+};

43. Multiply Strings/readme.md

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+模拟笔算的流程