diff --git a/atpg b/atpg
index 61b9f2d..6c33244 100755
Binary files a/atpg and b/atpg differ
diff --git a/circuit.cpp b/circuit.cpp
index e69de29..aa9ef8b 100644
--- a/circuit.cpp
+++ b/circuit.cpp
@@ -0,0 +1,30 @@
+#include "circuit.h"
+
+#include <queue>
+#include <unordered_map>
+
+void Circuit::cal_topo_index() {
+    int topo = 1;
+    std::queue<Gate*> q;
+
+    std::unordered_map<Gate*, int> ins;
+    for(Gate* gate : gates) {
+        ins[gate] = gate->inputs.size();
+    }
+
+    for(auto in : PIs) {
+        in->topo = topo++;
+        q.push(in);
+    }
+
+    while(!q.empty()) {
+        Gate* g = q.front(); q.pop();
+        for(Gate* out : g->outputs) {
+            ins[out]--;
+            if(ins[out] == 0) {
+                out->topo = topo++;
+                q.push(out);
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/circuit.h b/circuit.h
index eba71d0..a893714 100644
--- a/circuit.h
+++ b/circuit.h
@@ -4,6 +4,7 @@
 
 class Gate {
 public:
+    int topo;
     std::string name;
     enum { AND, NAND, OR, NOR, XOR, XNOR, NOT, BUF, INPUT, OUTPUT } type;
     enum { VAL_ZERO, VAL_ONE, VAL_X } value;
@@ -15,6 +16,9 @@ class Circuit {
 public:
 std::vector<Gate*> PIs;
 std::vector<Gate*> POs;
+std::vector<Gate*> gates;
 std::unordered_map<std::string, Gate*> name2gate;
 void parse_from_file(const char *filename);
+void cal_topo_index();
+void cal_headlines();
 };
\ No newline at end of file
diff --git a/main.cpp b/main.cpp
index 1a666f4..e1c8ad7 100644
--- a/main.cpp
+++ b/main.cpp
@@ -1,5 +1,6 @@
 #include <cstdio>
 #include <cstdlib>
+#include <assert.h>
 
 
 #include "circuit.h"
@@ -16,11 +17,15 @@ int main(int args, char* argv[]) {
     printf("parsing file %s...\n", argv[1]);
     circuit.parse_from_file(argv[1]);
     printf("====== Circuit Statistics ====== \n");
-    printf("PI:\t%d\n", circuit.PIs.size());
-    printf("PO:\t%d\n", circuit.POs.size());
-    printf("Gates:\t%d\n", circuit.name2gate.size());
+    printf("PI:\t%ld\n", circuit.PIs.size());
+    printf("PO:\t%ld\n", circuit.POs.size());
+    printf("Gates:\t%ld\n", circuit.name2gate.size());
 
-    
+    printf("cal topo index ...\n");
+    circuit.cal_topo_index();
+    for(Gate* gate : circuit.gates) {
+        assert(gate->topo > 0);
+    }
 
     return 0;
 }
\ No newline at end of file
diff --git a/makefile b/makefile
index 386f998..79aab05 100644
--- a/makefile
+++ b/makefile
@@ -7,7 +7,7 @@
 #编译工具用g++，以同时支持C和C++程序，以及二者的混合编译
 CC=g++
 
-CPPFLAGS=-O3
+CPPFLAGS=-O3 -std=c++17
  
 #使用$(winldcard *.c)来获取工作目录下的所有.c文件的列表
 #sources:=main.cpp command.c
diff --git a/parser.cpp b/parser.cpp
index 906798b..fe276e7 100644
--- a/parser.cpp
+++ b/parser.cpp
@@ -6,10 +6,23 @@
 #include <regex>
 #include <set>
 
-std::string trim(const std::string& s) {
-    auto wsfront = std::find_if_not(s.begin(), s.end(), [](int c){ return std::isspace(c); });
-    auto wsback = std::find_if_not(s.rbegin(), s.rend(), [](int c){ return std::isspace(c); }).base();
-    return (wsback <= wsfront ? std::string() : std::string(wsfront, wsback));
+void line2tokens(const std::string &line, std::vector<std::string> &tokens) {
+    std::string token;
+    for(char c : line) {
+        if(c == ' ' || c == '\t' || c == '\r' || c == '\n') continue;
+        if(c == '=' || c == ',' || c == '(' || c == ')') {
+            if(!token.size()) continue;
+            tokens.push_back(token);
+            token.clear(); token += c;
+            tokens.push_back(token);
+            token.clear();
+        } else {
+            token += c;
+        }
+    }
+    if(token.size()) {
+        tokens.push_back(token);
+    }
 }
 
 void Circuit::parse_from_file(const char *filename) {
@@ -23,79 +36,102 @@ void Circuit::parse_from_file(const char *filename) {
     // buf 10MB
     file.rdbuf()->pubsetbuf(0, 10 *1024 * 1024);
 
+    std::vector<std::string> bufPO;
+
     std::string line;
     while(std::getline(file, line)) {
         if(line[0] == '#') continue;
         if(line == "\r" || line == "") continue;
 
-        std::cmatch m;
-        if(std::regex_match(line.c_str(), m, std::regex("INPUT\\s*\\(\\s*(.*)\\s*\\)\\s*"))) {
+        std::vector<std::string> tokens;
 
-            Gate *input = new Gate();
-            input->name = m.str(1);
-            input->type = Gate::INPUT;
-            input->value = Gate::VAL_X;
-            name2gate.insert(std::make_pair(input->name, input));
+        line2tokens(line, tokens);
+        // std::cout << line << std::endl;
+        // std::cout << "tokens: ";
+        // for(auto &token : tokens) {
+        //     std::cout << "$" << token << "$ ";
+        // }
+        // std::cout << std::endl;        
 
+        // gate
+        if(tokens.size() >= 6 && tokens[1] == "=" && tokens[3] == "(" && tokens.back() == ")") {
+            std::vector<std::string> ins;
 
-            std::cout << "input -> $" << input->name << "$" << std::endl;
-
-            PIs.push_back(input);
-        } else if(std::regex_match(line.c_str(), m, std::regex("OUTPUT\\s*\\(\\s*(.*)\\s*\\)\\s*"))) {
-
-            Gate *output = new Gate();
-            output->name = m.str(1);
-            output->type = Gate::OUTPUT;
-            output->value = Gate::VAL_X;
-            name2gate.insert(std::make_pair(output->name, output));
-
-            POs.push_back(output);
-        } else if(std::regex_match(line.c_str(), m, std::regex("\\s*(\\S+)\\s*=\\s*(\\w+)\\s*\\(\\s*(.*)\\s*\\)\\s*"))) {
-
-            std::string output_name = m.str(1);
-            std::string gate_name = m.str(2);
-            std::string list = m.str(3);
-
-            Gate *gate = new Gate();
-
-            gate->name = output_name;
-            gate->value = Gate::VAL_X;
-
-            name2gate.insert(std::make_pair(gate->name, gate));
-
-            // split by ","
-            std::regex pattern(R"(\s*,\s*)");
-            std::sregex_token_iterator it(list.begin(), list.end(), pattern, -1);
-            std::sregex_token_iterator end;
-
-            while (it != end) {
-                std::string in = trim(*it++);
-                if(!name2gate.count(in)) {
-                    printf("Error while reading file: $%s$ is not defined before used.\n", in.c_str());
+            for(int i=4; i<tokens.size()-1; i+=2) {
+                if(tokens[i] == ",") {
+                    printf("Error while reading line: %s\n", line.c_str());
                     exit(1);
                 }
-                Gate* in_gate = name2gate[in];
+                ins.push_back(tokens[i]);
+            }
+            for(int i=5; i<tokens.size()-1; i+=2) {
+                if(tokens[i] != ",") {
+                    printf("Error while reading line: %s\n", line.c_str());
+                    exit(1);
+                }
+            }
+
+            Gate* gate = new Gate();
+            gate->name = tokens[0];
+            gate->value = Gate::VAL_X;
+
+            for(auto &in : ins) {
+                if(!name2gate.count(in)) {
+                    printf("Error while reading file: gate %s used before defination.\n", in.c_str());
+                    exit(1);
+                }
+
+                auto in_gate = name2gate[in];
 
                 gate->inputs.push_back(in_gate);
                 in_gate->outputs.push_back(gate);
             }
 
-            if(gate_name == "AND") { gate->type = Gate::AND; }
-            else if(gate_name == "NAND") { gate->type = Gate::NAND; }
-            else if(gate_name == "OR") { gate->type = Gate::OR; }
-            else if(gate_name == "NOR") { gate->type = Gate::NOR; }
-            else if(gate_name == "XOR") { gate->type = Gate::XOR; }
-            else if(gate_name == "XNOR") { gate->type = Gate::XNOR; }
-            else if(gate_name == "NOT") { gate->type = Gate::NOT; }
-            else if(gate_name == "BUF") { gate->type = Gate::BUF; }
+            if(tokens[2] == "AND") { gate->type = Gate::AND; }
+            else if(tokens[2] == "NAND") { gate->type = Gate::NAND; }
+            else if(tokens[2] == "OR") { gate->type = Gate::OR; }
+            else if(tokens[2] == "NOR") { gate->type = Gate::NOR; }
+            else if(tokens[2] == "XOR") { gate->type = Gate::XOR; }
+            else if(tokens[2] == "XNOR") { gate->type = Gate::XNOR; }
+            else if(tokens[2] == "NOT") { gate->type = Gate::NOT; }
+            else if(tokens[2] == "BUFF") { gate->type = Gate::BUF; }
+            else if(tokens[2] == "BUF") { gate->type = Gate::BUF; }
             else {
-                printf("Error while reading file: %s is not a valid gate.\n", gate_name.c_str());
+                printf("Error while reading file: %s is not a valid gate.\n", tokens[2].c_str());
                 exit(1);
             }
 
-       } else {
-            printf("Error while reading file: \"%s\" is a wrong line.\n", line.c_str());
+            name2gate.insert(std::make_pair(gate->name, gate));
+            gates.push_back(gate);
+        }
+        // input
+        else if(tokens.size() == 4 && tokens[0] == "INPUT" && tokens[1] == "(" && tokens[3] == ")") {
+            Gate* gate = new Gate();
+            gate->name = tokens[2];
+            gate->type = Gate::INPUT;
+            gate->value = Gate::VAL_X;
+
+            name2gate.insert(std::make_pair(gate->name, gate));
+            gates.push_back(gate);
+            PIs.push_back(gate);
+        } 
+        // gate
+        else if(tokens.size() == 4 && tokens[0] == "OUTPUT" && tokens[1] == "(" && tokens[3] == ")") {
+            bufPO.push_back(tokens[2]);
+        }
+        // invalid line
+        else {
+            printf("Error while reading line: %s\n", line.c_str());
             exit(1);
-       }
+        }
+    }
+
+    // handle PO
+    for(auto& po_name : bufPO) {
+        if(!name2gate.count(po_name)) {
+            printf("Error while reading file: po %s is not a exist gate.\n", po_name.c_str());
+            exit(1);
+        }
+        POs.push_back(name2gate[po_name]);
     }
 }
\ No newline at end of file
diff --git a/res.txt b/res.txt
new file mode 100644
index 0000000..66b69eb
--- /dev/null
+++ b/res.txt
@@ -0,0 +1,90 @@
+parsing file c432.bench...
+INPUT(1)
+tokens: $INPUT$ $($ $1$ $)$ 
+INPUT(4)
+tokens: $INPUT$ $($ $4$ $)$ 
+INPUT(8)
+tokens: $INPUT$ $($ $8$ $)$ 
+INPUT(11)
+tokens: $INPUT$ $($ $11$ $)$ 
+INPUT(14)
+tokens: $INPUT$ $($ $14$ $)$ 
+INPUT(17)
+tokens: $INPUT$ $($ $17$ $)$ 
+INPUT(21)
+tokens: $INPUT$ $($ $21$ $)$ 
+INPUT(24)
+tokens: $INPUT$ $($ $24$ $)$ 
+INPUT(27)
+tokens: $INPUT$ $($ $27$ $)$ 
+INPUT(30)
+tokens: $INPUT$ $($ $30$ $)$ 
+INPUT(34)
+tokens: $INPUT$ $($ $34$ $)$ 
+INPUT(37)
+tokens: $INPUT$ $($ $37$ $)$ 
+INPUT(40)
+tokens: $INPUT$ $($ $40$ $)$ 
+INPUT(43)
+tokens: $INPUT$ $($ $43$ $)$ 
+INPUT(47)
+tokens: $INPUT$ $($ $47$ $)$ 
+INPUT(50)
+tokens: $INPUT$ $($ $50$ $)$ 
+INPUT(53)
+tokens: $INPUT$ $($ $53$ $)$ 
+INPUT(56)
+tokens: $INPUT$ $($ $56$ $)$ 
+INPUT(60)
+tokens: $INPUT$ $($ $60$ $)$ 
+INPUT(63)
+tokens: $INPUT$ $($ $63$ $)$ 
+INPUT(66)
+tokens: $INPUT$ $($ $66$ $)$ 
+INPUT(69)
+tokens: $INPUT$ $($ $69$ $)$ 
+INPUT(73)
+tokens: $INPUT$ $($ $73$ $)$ 
+INPUT(76)
+tokens: $INPUT$ $($ $76$ $)$ 
+INPUT(79)
+tokens: $INPUT$ $($ $79$ $)$ 
+INPUT(82)
+tokens: $INPUT$ $($ $82$ $)$ 
+INPUT(86)
+tokens: $INPUT$ $($ $86$ $)$ 
+INPUT(89)
+tokens: $INPUT$ $($ $89$ $)$ 
+INPUT(92)
+tokens: $INPUT$ $($ $92$ $)$ 
+INPUT(95)
+tokens: $INPUT$ $($ $95$ $)$ 
+INPUT(99)
+tokens: $INPUT$ $($ $99$ $)$ 
+INPUT(102)
+tokens: $INPUT$ $($ $102$ $)$ 
+INPUT(105)
+tokens: $INPUT$ $($ $105$ $)$ 
+INPUT(108)
+tokens: $INPUT$ $($ $108$ $)$ 
+INPUT(112)
+tokens: $INPUT$ $($ $112$ $)$ 
+INPUT(115)
+tokens: $INPUT$ $($ $115$ $)$ 
+OUTPUT(223)
+tokens: $OUTPUT$ $($ $223$ $)$ 
+OUTPUT(329)
+tokens: $OUTPUT$ $($ $329$ $)$ 
+OUTPUT(370)
+tokens: $OUTPUT$ $($ $370$ $)$ 
+OUTPUT(421)
+tokens: $OUTPUT$ $($ $421$ $)$ 
+OUTPUT(430)
+tokens: $OUTPUT$ $($ $430$ $)$ 
+OUTPUT(431)
+tokens: $OUTPUT$ $($ $431$ $)$ 
+OUTPUT(432)
+tokens: $OUTPUT$ $($ $432$ $)$ 
+118 = NOT(1)
+tokens: $118$ $=$ $NOT$ $($ $1$ $)$ 
+Error while reading line: 118 = NOT(1)