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在 Git 中，有四种 diff 算法，即 Myers、Minimal、Patience 和 Histogram，用于获取位于两个不同 commit 中的两个相同文件的差异。
Myers算法实现参考：
Myers‘Diff之贪婪算法_myers算法-CSDN博客
Git Diff 算法详解：Myers Diff Algorithm-腾讯云开发者社区-腾讯云 (tencent.com)
Myers差分算法的理解、实现、可视化 - Oto_G - 博客园 (cnblogs.com)
最后找到一个c++可用的代码如下，在Myers函数中传入两个需要比较的文档内容。
#include <QDir>
#include <QVariantMap>
#include <QVariantList>
#include <QStringList>
#include <QList>
#include <QDebug>namespace ScriptManagerWebNew {
enum MoveType {MoveType_None,MoveType_Down,MoveType_Right,MoveType_Diagonal
};
struct Point {Point(int x, int y) {this->x = x;this->y = y;}bool operator== (const Point& pt) const {return this->x == pt.x && this->y == pt.y;}bool operator!= (const Point& pt) const {return this->x != pt.x || this->y != pt.y;}MoveType operator >(const Point& pt2) {if (this->x == pt2.x && this->y + 1 == pt2.y) {return MoveType_Down;}else if (this->y == pt2.y && this->x + 1 == pt2.x) {return MoveType_Right;}else if (this->x + 1 == pt2.x && this->y + 1 == pt2.y) {return MoveType_Diagonal;}return MoveType_None;}int x = 0;int y = 0;
};QString Myers(QString formerText, QString currentText)
{const auto lines = formerText.split("\n");const auto lines2 = currentText.split("\n");auto n = lines.size();auto m = lines2.size();std::vector<std::map<int, int>> Xlist;//只存储x坐标,y可以由k=x-y算出std::map<int,int> X;//假设起始点(0,-1)X[1] = 0;bool go_ahead = true;//步数d//从0开始，因为d=0时，也可能沿对角线前进for (int d = 0; d <= n + m && go_ahead; d++) {//k-lines: k has odd or even values according to an odd or even dfor (int k = -d; k <= d; k = k + 2) {//判断该从(d-1,k-1)向右走，还是从(d-1,k+1)向下走//当k!=d && k!=-d时, 可以从X[k + 1]向下走, 或者X[k - 1]向右走//具体怎么选择，判断x值：选择x大的,保证删除操作优于添加操作bool down = (k == -d || (k != d && X[k - 1] < X[k + 1]));int kPrev = down ? k + 1 : k - 1;//起始位置int xStart = X[kPrev];int yStart = xStart - kPrev;//中间位置int xTmp = down ? xStart : xStart + 1;int yTmp = xTmp - k;//此次move后的位置int xEnd = xTmp;int yEnd = yTmp;//判断能否总对角线(moving through a diagonal is free)while (xEnd < n && yEnd < m && lines[xEnd] == lines2[yEnd]) {++xEnd;++yEnd;}X[k] = xEnd;//到终点,找到了最短路线if (xEnd >= n && yEnd >= m) {go_ahead = false;break;}}Xlist.push_back(X);}//回退，从终点到起点，找出路线std::vector<Point> path; //move的路线Point pt(lines.length(), lines2.length());path.push_back(pt);for (int d = Xlist.size() - 1; pt.x > 0 || pt.y > 0; --d) {auto X = Xlist[d];int k = pt.x - pt.y;//结束位置int xEnd = X[k];int yEnd = pt.x - k;//结束位置前是否走的对角线while (xEnd > 0 && yEnd > 0 && xEnd <= n && yEnd <= m && lines[xEnd-1] == lines2[yEnd-1]) {--xEnd;--yEnd;path.push_back(Point(xEnd, yEnd));}//down可以确定上一步的k线，对角线上的移动不影响d和k//并且,Xlist[d][k-1] == Xlist[d-1][k-1]; Xlist[d][k+1] == Xlist[d-1][k+1]bool down = (k == -d || (k != d && X[k - 1] < X[k + 1]));int kPrev = down ? k + 1 : k - 1;//起始位置int xStart = X[kPrev];int yStart = xStart - kPrev;中间位置//int xTmp = down ? xStart : xStart + 1;//int yTmp = xTmp - k;path.push_back(Point(xStart, yStart));pt.x = xStart;pt.y = yStart;}path.pop_back();//path第一个点是假设的起点(0,-1);//文字描述path代表的操作QString stream;
// std::stringstream stream;if (path.size() >= 2) {int size = path.size();for (int i = size - 2; i >= 0; --i) {Point prev_point = path[i+1];MoveType type = prev_point>(path[i]);switch (type) {case MoveType_Right: {stream.append("-" + lines[prev_point.x]+"\n");break;}case MoveType_Down: {stream.append( "+" + lines2[prev_point.y]+"\n");break;}case MoveType_Diagonal: {stream.append(lines[prev_point.x]+"\n");break;}}}}
// std::cout << "最短编辑路线如下：" << std::endl;
// std::cout << stream.str();
// std::string input;
// std::cin >> input;return stream;
}
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