Create 640-solve-the-equation.js

Author: everthis

640-solve-the-equation.js

@@ -0,0 +1,58 @@
+/**
+ * @param {string} equation
+ * @return {string}
+ */
+function solveEquation (equation) {
+  const strArr = equation.split('=')
+  const leftHash = build(strArr[0])
+  const rightHash = build(strArr[1])
+  const xnum = leftHash.x - rightHash.x
+  const num = rightHash.num - leftHash.num
+  if(xnum === 0 && num !== 0) {
+     return "No solution"
+  } else if(xnum === 0) {
+     return "Infinite solutions"
+  } else {
+     return `x=${num / xnum}`
+  }
+};
+
+function build(str) {
+  let cur = ''
+  const map = {
+    num:0,
+    x:0
+  }
+  for(let i = 0; i < str.length; i++) {
+    if(str[i] === '-' || str[i] === '+') {
+      chkCur(cur, map)
+      cur = str[i]
+    } else {
+      cur += str[i]
+    }
+  }
+  if(cur !== '') {
+    chkCur(cur, map)
+  }
+  return map
+}
+function chkCur(cur, map) {
+  let xIdx = cur.indexOf('x')
+  if(xIdx === -1) {
+    map.num += +cur
+  } else {
+    map.x += chkX(cur, xIdx)
+  }
+}
+function chkX(str, xIdx) {
+  let tmp = str.slice(0,xIdx)
+  let num = 0
+  if(tmp === '-') {
+    num = -1
+  } else if(tmp === '' || tmp === '+') {
+    num = 1
+  } else {
+    num = +tmp
+  }
+  return num
+}