生活随笔
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并查集 - 除法求值
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題目鏈接
將所有等式關系轉化為同一變量的倍數。
class Solution {
public:vector
<double> calcEquation(vector
<vector
<string
>>& equations
, vector
<double>& values
, vector
<vector
<string
>>& queries
) {int n
= equations
.size(), q
= queries
.size();vector
<double> ret
, fa(n
*2), weight(n
*2, 1.0);for (int i
= 0; i
< n
*2; ++i
) {fa
[i
] = i
;}map
<string
, int> num
;int now
= 0;for (int i
= 0; i
< n
; ++i
) {if (num
.find(equations
[i
][0]) == num
.end()) {num
[equations
[i
][0]] = now
++;}if (num
.find(equations
[i
][1]) == num
.end()) {num
[equations
[i
][1]] = now
++;}int x
= num
[equations
[i
][0]];int y
= num
[equations
[i
][1]];int fx
= find(fa
, weight
, x
);int fy
= find(fa
, weight
, y
);fa
[fx
] = fy
;weight
[fx
] = weight
[y
] / weight
[x
] * values
[i
];}for (int i
= 0; i
< q
; ++i
) {if (num
.find(queries
[i
][0]) == num
.end() || num
.find(queries
[i
][1]) == num
.end()) {ret
.push_back(-1);continue;}int x
= num
[queries
[i
][0]];int y
= num
[queries
[i
][1]];int fx
= find(fa
, weight
, x
);int fy
= find(fa
, weight
, y
);if (fx
!= fy
) {ret
.push_back(-1);}else {ret
.push_back(weight
[x
] / weight
[y
]);}}return ret
;}int find(vector
<double> &fa
, vector
<double> &weight
, int x
) {if (fa
[x
] != x
) {int rt
= find(fa
, weight
, fa
[x
]);weight
[x
] *= weight
[fa
[x
]];fa
[x
] = rt
;}return fa
[x
];}
};
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