string能否作为函数的形参？ 出错：std:out_of_range 和 Run-Time Check Failure #0,该怎么解决

//BM

#include <cstdio>
#include <iostream>
#include <string>
//#pragma comment(lib,"**.lib")

using namespace std;

string cShiftTable(string mode, string text);
string cSuffTable(string mode);
int BM(string mode, string text);

int main(){
    int location = -1;    
    string mode, text;

    cout << "请输入模式字符串:" << endl;
    getline(cin, mode);
    cout << "请输入文本：" << endl;
    getline(cin, text);

    location = BM(mode, text);
    if(location == -1){
        cout << "模式在文本中不存在！" << endl;
    }
    else {
        cout << "模式在文本中的位置为：" + location << endl;
    }
    return 0;
}

//int BM(const char * a, const char * b){
int BM(string mode, string text){
    //string mode(a), text(b);
    int m = mode.length(), t = text.length();
    int d = 0, d1 = 0, d2 = 0;
    int PText = 0, PMode = 0, MatchCount = 0;
    string ShiftTable, SuffTable;
    ShiftTable = cShiftTable(mode, text);             //生成坏符号移动表
    SuffTable = cSuffTable(mode);                     //生成好后缀移动表
    while(PText < t-m){
        PMode = m-1;
        while( (PMode >= 0) && mode.at(PMode) == text.at(PText+PMode)){
            try {
                mode.at(PMode);  
                text.at(PText+PMode);
            }  
            catch (std::out_of_range &exc) {  
                std::cerr << exc.what() << " Line:" << __LINE__ << " File:" << __FILE__ << endl;  
            }  
            MatchCount += 1;
            PMode--;
        }
        if(MatchCount == m){
            return PText;
        }
        else{
            try {
                ShiftTable.at( mode.at(m-MatchCount-1));  
                SuffTable.at(MatchCount);
            }  
            catch (std::out_of_range &exc) {  
                std::cerr << exc.what() << " Line:" << __LINE__ << " File:" << __FILE__ << endl;  
            } 
            d1 = max( int(ShiftTable.at( mode.at(m-MatchCount-1))) - MatchCount, 1);
            d2 = SuffTable.at(MatchCount);
            d = max(d1, d2);
            PText += d;
        }
    }
    return -1;
}


string cShiftTable(string mode,string text){
    int i = 0, Max = 0;
    int m = mode.length();
    int t = text.length();
    for(i = 0;i < m-1;i++){
        try {
            mode.at(i);
        }  
        catch (std::out_of_range &exc) {  
            std::cerr << exc.what() << " Line:" << __LINE__ << " File:" << __FILE__ << endl;  
        }
        if(mode.at(i) < mode.at(i+1))  Max = i+1;
    }

    string ShiftTable(int (mode.at(Max)), m);

    for(i = 0;i < m;i++){
        ShiftTable.at( mode.at(i)) = m-i-1;
    }
    return ShiftTable;
}

string cSuffTable(string mode){
    int i = 0, j = 0;
    int m = mode.length();
    string SuffTable(m-1, m);
    for(i = 1;i < m;i++){
        string Suff(mode, m-i, i);
        for(j = m-i-i;j > i-1;j--){
            string Compare(mode, j, i);
            if(Compare == Suff){
                SuffTable.at(i) = m-j-i;            
            }
        }
    }
    return SuffTable;
}