102 lines
3.8 KiB
Rust
102 lines
3.8 KiB
Rust
use std::fmt::format;
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use crate::Solution;
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impl Solution {
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/// [640.求解方程](https://leetcode.cn/problems/solve-the-equation/)
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///
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/// 2022-08-09 14:19:01
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///
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/// 求解一个给定的方程，将`x`以字符串 `"x=#value"` 的形式返回。该方程仅包含 `'+'` ， `'-'` 操作，变量 `x` 和其对应系数。
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///
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/// 如果方程没有解，请返回 `"No solution"` 。如果方程有无限解，则返回 `“Infinite solutions”` 。
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///
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/// 如果方程中只有一个解，要保证返回值 'x' 是一个整数。
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///
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/// + **示例 1：**
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/// + **输入:** equation = "x+5-3+x=6+x-2"
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/// + **输出:** "x=2"
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/// + **示例 2:**
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/// + **输入:** equation = "x=x"
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/// + **输出:** "Infinite solutions"
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/// + **示例 3:**
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/// + **输入:** equation = "2x=x"
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/// + **输出:** "x=0"
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/// + **提示:**
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/// * `3 <= equation.length <= 1000`
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/// * `equation` 只有一个 `'='`.
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/// * `equation` 方程由整数组成，其绝对值在 `[0, 100]` 范围内，不含前导零和变量 `'x'` 。
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/// + Related Topics
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/// * 数学
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/// * 字符串
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/// * 模拟
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pub fn solve_equation(equation: String) -> String {
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/*let (mut a,mut b,mut c) = (0, 0, 0);
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let mut sign = 1;
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let mut left = 1;
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let mut has_c = false;
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for z in equation.into_bytes() {
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match z {
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b'x' => {
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a += if has_c { sign * left * c } else { sign * left };
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c = 0;
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has_c = false;
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}
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b'+' => {
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b += sign * left * c;
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c = 0;
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sign = 1;
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has_c = false;
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}
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b'-' => {
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b += sign * left * c;
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c = 0;
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sign = -1;
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has_c = false;
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}
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b'=' => {
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b += sign * left * c;
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c = 0;
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sign = 1;
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left = -1;
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has_c = false;
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}
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_ => {
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c = c * 10 + (z - b'0') as i32;
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has_c = true;
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}
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}
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}
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b += sign * left * c;
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match (a, b) {
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(0, 0) => "Infinite solutions".to_owned(),
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(0, _) => "No solution".to_owned(),
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_ => format!("x={}", -b / a)
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}*/
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match equation.into_bytes().into_iter().fold((0, 0, 0, 1, 1, false), |(a, b, c, sign, left, has_c), z| match z {
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b'x' => (a + if has_c { sign * left * c } else { sign * left }, b, 0, sign, left, false),
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b'+' => (a, b + sign * left * c, 0, 1, left, false),
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b'-' => (a, b + sign * left * c, 0, -1, left, false),
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b'=' => (a, b + sign * left * c, 0, 1, -1, false),
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_ => (a, b, c * 10 + (z - b'0') as i32, sign, left, true)
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}) {
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(a, b, c, sign, left, _) => match (a, b + sign * left * c) {
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(a, b) => if a == 0 { if b == 0 { "Infinite solutions".to_owned() } else { "No solution".to_owned() } } else { format!("x={}", -b / a) }
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}
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}
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}
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}
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#[cfg(test)]
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mod test {
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use crate::Solution;
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#[test]
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fn test_q0640() {
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assert_eq!(Solution::solve_equation("x+5-3+x=6+x-2".to_owned()), "x=2".to_owned());
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assert_eq!(Solution::solve_equation("x=x".to_owned()), "Infinite solutions".to_owned());
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assert_eq!(Solution::solve_equation("2x=x".to_owned()), "x=0".to_owned());
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assert_eq!(Solution::solve_equation("0x=0".to_owned()), "Infinite solutions".to_owned());
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assert_eq!(Solution::solve_equation("0=0x".to_owned()), "Infinite solutions".to_owned());
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}
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}
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