640.Solve-the-Equation
640. Solve the Equation
้ข็ฎๅฐๅ
https://leetcode.com/problems/solve-the-equation/
้ข็ฎๆ่ฟฐ
Solve a given equation and return the value of x in the form of string "x=#value". The equation contains only '+', '-' operation, the variable x and its coefficient.
If there is no solution for the equation, return "No solution".
If there are infinite solutions for the equation, return "Infinite solutions".
If there is exactly one solution for the equation, we ensure that the value of x is an integer.
Example 1:
Input: "x+5-3+x=6+x-2"
Output: "x=2"
Example 2:
Input: "x=x"
Output: "Infinite solutions"
Example 3:
Input: "2x=x"
Output: "x=0"
Example 4:
Input: "2x+3x-6x=x+2"
Output: "x=-1"
Example 5:
Input: "x=x+2"
Output: "No solution"
ไปฃ็
Approach 1: Partioning Coefficients
ๅทฆ่พนๅ้ = ๅณ่พนๅธธๆฐ
x = ๅณ่พน/ๅทฆ่พน
Time complexity : O(n)
Space complexity : O(n)
class Solution {
public String solveEquation(String equation) {
String[] lr = equation.split("=");
int lhs = 0, rhs = 0;
for (String x: breakIt(lr[0])) {
if (x.indexOf("x") >= 0) {
lhs += Integer.parseInt(coeff(x));
} else {
rhs -= Integer.parseInt(x);
}
}
for (String x: breakIt(lr[1])) {
if (x.indexOf("x") >= 0)
lhs -= Integer.parseInt(coeff(x));
else
rhs += Integer.parseInt(x);
}
if (lhs == 0) {
if (rhs == 0) {
return "Infinite solutions";
} else {
return "No solution";
}
}
return "x=" + rhs / lhs;
}
public List<String> breakIt(String s) {
List<String> res = new ArrayList<>();
String r = "";
for (int i = 0; i < s.length(); i++) {
if (s.charAt(i) == '+' || s.charAt(i) == '-') {
if (r.length() > 0) { // ๅๅฒ
res.add(r);
}
r = "" + s.charAt(i);
} else {
r += s.charAt(i);
}
}
res.add(r);
return res;
}
public String coeff(String x) {
if (x.length() > 1 && x.charAt(x.length() - 2) >= '0' && x.charAt(x.length() - 2) <= '9') {
return x.replace("x", "");
} else {
return x.replace("x", "1");
}
}
}
Approach #2 Using regex for spliting
class Solution {
public String coeff(String x) {
if (x.length() > 1 && x.charAt(x.length() - 2) >= '0' && x.charAt(x.length() - 2) <= '9')
return x.replace("x", "");
return x.replace("x", "1");
}
public String solveEquation(String equation) {
String[] lr = equation.split("=");
int lhs = 0, rhs = 0;
for (String x: lr[0].split("(?=\\+)|(?=-)")) {
if (x.indexOf("x") >= 0) {
lhs += Integer.parseInt(coeff(x));
} else
rhs -= Integer.parseInt(x);
}
for (String x: lr[1].split("(?=\\+)|(?=-)")) {
if (x.indexOf("x") >= 0)
lhs -= Integer.parseInt(coeff(x));
else
rhs += Integer.parseInt(x);
}
if (lhs == 0) {
if (rhs == 0)
return "Infinite solutions";
else
return "No solution";
} else
return "x=" + rhs / lhs;
}
}
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