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package math;

/**

* Created by gouthamvidyapradhan on 16/02/2018. 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.

*

* <p>If there is no solution for the equation, return "No solution".

*

* <p>If there are infinite solutions for the equation, return "Infinite solutions".

*

* <p>If there is exactly one solution for the equation, we ensure that the value of x is an

* integer.

*

* <p>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"

*

* <p>Solution: Solve the left and right part separately and then sum up the results.

*/

public class SolveTheEquation {

int xL = 0, xR = 0, tL = 0, tR = 0;

public static void main(String[] args) throws Exception {

System.out.println(new SolveTheEquation().solveEquation("x=x+2"));

}

public String solveEquation(String equation) {

String[] parts = equation.split("=");

solve(parts[0], true);

solve(parts[1], false);

long right = (long) tR - tL;

long left = (long) xL - xR;

if (left == 0 && right == 0) {

return "Infinite solutions";

} else if (left == 0) {

return "No solution";

} else if (right == 0) {

return "x=0";

} else {

return "x=" + (right / left);

}

}

private void solve(String s, boolean isLeft) {

String num = "";

int xSum = 0;

int rest = 0;

boolean isNeg = false;

for (int i = 0; i < s.length(); i++) {

char c = s.charAt(i);

if (c == '-') {

if (!num.isEmpty()) {

xSum = calculate(num, isNeg, xSum, rest)[0];

rest = calculate(num, isNeg, xSum, rest)[1];

}

isNeg = true;

num = "";

} else if (c == '+') {

if (!num.isEmpty()) {

xSum = calculate(num, isNeg, xSum, rest)[0];

rest = calculate(num, isNeg, xSum, rest)[1];

}

isNeg = false;

num = "";

} else {

num += c;

}

}

if (!num.isEmpty()) {

xSum = calculate(num, isNeg, xSum, rest)[0];

rest = calculate(num, isNeg, xSum, rest)[1];

}

if (isLeft) {

xL = xSum;

tL = rest;

} else {

xR = xSum;

tR = rest;

}

}

private int[] calculate(String num, boolean isNeg, int xSum, int rest) {

int[] A = new int[2];

if (num.contains("x")) {

num = num.substring(0, num.length() - 1);

if (isNeg) {

xSum -= num.isEmpty() ? 1 : Integer.parseInt(num);

} else {

xSum += num.isEmpty() ? 1 : Integer.parseInt(num);

}

} else {

if (isNeg) {

rest -= Integer.parseInt(num);

} else {

rest += Integer.parseInt(num);

}

}

A[0] = xSum;

A[1] = rest;

return A;

}

}