vector 排序

vector排序，只要 #include <algorithm>
利用sort這function就可以了。

簡單的vector

vector <int> temp;
temp.push_back(2);
temp.push_back(4);
temp.push_back(6);

sort(temp.begin(),temp.end());

結果就是由小排到大。
可是如果 vector 存的是 struct ，就得要多寫一個比較的function

typedef struct Freqamp{
    double freq;
    double amp;
}FREQAMP;

bool struct_cmp_by_freq(FREQAMP a, FREQAMP b)
{
    return a.freq < b.freq;
}

main()
{
    vector <FREQAMP> temp;
    FREQAMP freqAMP;

    freqAMP.freq = 330;
    freqAMP.amp = 117.56;
    temp.push_back(freqAMP);

    freqAMP.freq = 450;
    freqAMP.amp = 99.56;
    temp.push_back(freqAMP);

    freqAMP.freq = 110;
    freqAMP.amp = 106.56;
    temp.push_back(freqAMP);
 
    sort(temp.begin(),temp.end(), struct_cmp_by_freq);
}

就可以針對其中一項下去排序，不過要注意 sort 是當 compare 為 false 時做swap。

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